Chemistry Exam 2

Front 1

The Atomic Theory chemical principle

Back 1

Democritus and Leucippus, ancient Greek philosophers, were the first to assert that matter is ultijmately composed of small, indestructible particles. It was not until 2000 years later, however, that john Dalton introduced a formal atomic theory stating that matter is composed of atoms; atoms of a given element have unique properties that distinguish them from atoms of other elements; and atoms combine in simple, whole number ratios to form compounds,.

Front 2

The atomic theory relevance

Back 2

This is important because it explains the physical world. You and everything you see are made of atoms. To understand the world, we must begin by understanding atoms because they determine the properties of matter.

Front 3

Chemical Principle: Discovery of the atom's nucleus

Back 3

Rutherford's gold foil experiment probed atomic structure, and his results led to the nuclear model of the atom, which, with minor modifications to accommodate neutrons, is still valid today. In this model, the atom is composed of protons and neutrons--which compose most of the atom's mass and are grouped together in a dense nucleus--and electrons, which compose most of the atom's volume. Protons and neutrons have similar amu 1 and electrons are much smaller .00055 amu

Front 4

Why is the discovery of the nucleus importatn?

Back 4

We can see why it is relevane by asking what if it where otherwise? What if matter were NOT mostly empty space? While we cannot know for certain, it seems probable that such matter would not form the diversity of substances required for life--and then, of course, we would not be around to ask the question.

Front 5

Chenical principle: Charge

Back 5

Protons and electrons both have electrical charges. Protons are +1 and electron is -1. Neutrons are neutral and have no charge. When protons and electrons combine in atoms, their charges cancel

Front 6

why is electrical charge relevant in our world?

Back 6

Many of the machines and compu\ters we depend on are powered by electricity. This is simply the movement of electrical charge.

Front 7

Chenical Principle: Atomic number

Back 7

The characteristic that defines an element is the number of protons in the nuclei of its atoms; this number is called the atomic number (Z). Elements are the fundamental building blocks from which all compounds are made.

Front 8

Chemical PRinciple: Ions

Back 8

When an atom gains or loses electrons, it becomes an ion. Positively charged ions are called cations, and negatively charged ions are callled anions. Cations and anions occur together so that matter is ordinarily charge-neutral.

Front 9

Chemical principles: Isotopes

Back 9

While all atoms of a given element have the same number of protons, they do not necessarily have the same number of neutrons. Atoms of the same element with different numbers of neutrons are called isotopes. Isotopes are characterized by their mass bumber (A), the sum of the number of protons and their mass number of neutronjs inn their nucleus. Each naturally occurring sample of an element has the same percent natural abundance of each isotope. These percentages together with the mass of each isotope are used to compute the atomic mass of the element, a weighted average of the masses of the individual isotopes.

Front 10

Why is it important to understand atoms?

Back 10

Because atoms make up everything around us. In order to understand the world around us we must understand atoms.

Front 11

What is an atom?

Back 11

An atom is the smallest identifiable unit of an element.

Front 12

What did democritus contribute to our modern understanding of matter?

Back 12

Suggested if you divide matter into smaller and smaller pieces, you will eventually end up with tiny, indestructible particles, atoms.

Front 13

What are the three main ideas in Dalton's atomic theory?

Back 13

1. Each element is composed of tiny, indestructible particles called atoms.
2. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
3. Atoms combine in simple whole number ratios.

Front 14

Describe Rutherford's gold foil experiment and the results of it. How did these results contradict the plum pudding model of the atom?

Back 14

Rutherford's experiment involved sending positively charged alpha particles through a thin sheet of gold foil and detecting if there was any deflection of the particles. He found that most passed straight through, yet some particles showed some deflection. This result contradicts the plum pudding model of the atom because the plum pudding model doesn't explain the deflection of alpha particles.

Front 15

What are the main ideas in the nuclear theory of the atom?

Back 15

1. Most of the atom's mass and all of its positive charge are contained in a small core called the nucleus.
2. Most of the volume of the atom is empty space through which the tiny, negatively charged electrons are dispersed.
3. There are as many negatively charged electrons outside the nucleus as there are positively charged particles (protons inside the nucleus, so that the atom is electrically neutral.

Front 16

What is electrical charge

Back 16

Electrical charge is a fundamental property of protons and electrons. Positive and negative attract. Positive positive repel. Negative negative repel. Positive and neg charges cancel each other out so a proton and electron, when paired, are charge neutral.

Front 17

Subatomic particles and their masses and charges

Back 17

Proton--Mass kg. 1.67262x10-27 kg 1 amu +1
Neutron 1.67262x10-27 kg. 1 amu 0
Electron .00091x10-27 .00055amu -1

Front 18

Is matter usually electrically charged? How would matter be different if it were not electrically charged?

Back 18

Yes it is because pos and neg attract. If they didn't then we'd have random objects attracting and repelling one another.

Front 19

What does the atomic number of an element specify?

Back 19

It is represented with the letter (Z) and specifies the number of protons.

Front 20

What is a chemical symbol?

Back 20

A chemical symbol is a unique one or two letter abbreviation for an element. It is listed below the atomic number of that element on the periodic table.

Front 21

Give some examples of how elements got their names.

Back 21

Most are based on the english name of the element. However some have symbols based on their latin names such as potassium is K from the latin kalium. Sodium Na is from latin natrium. Lead latin plumbum Pb. Iron Fe latin ferrum copper Cu cuprum

Front 22

What was Dmitri Mendeleev's main contribution to our modern understanding of chemistry?

Back 22

He began the organization of the periodic table. He noticed that when elements are arranged in order of increasing relative mass, certain sets of properties recur periodically.

Front 23

Metals characteristics and where they are found and examples of metals

Back 23

Metals are found on the left side of the periodic table. They are good conductors of electricity and heat; they can be pounded into flat sheets (malleability); they can be drawn into wires; they are often shiny; and they tend to lose electrons when they undergo chemical changes examples of metals are iron, magnesium, and sodium.

Front 24

Nonmetals where they're found, characteristics, and examples

Back 24

Nonmetals occupy the upper right side of the periodic table above the metalloids. Some are solids at room temp. Others are gasses, They tend to be poor conductors of heat and electricity and tend to gain electrons when they undergo chemical changes. Examples are oxygen, nitrogen, chlorine, and iodine.

Front 25

Metalloids where they're found and their uses. Examples

Back 25

Found along the zigzag diagonal line show mixed properties. They have electrical conductivity which can be changed and controlled. They are used in computers, cell phones, and many other modern gadgets. Examples: silicon, arsenic, and germanium.

Front 26

Transition elements

Back 26

properties are less predictable based on their position in the periodic table.

Front 27

Noble gasses: location

Back 27

Noble gasses are chemically gases. Helium is the most familiar. Chemically stable gases.

Front 28

Alkali metals

Back 28

Group 1A elements. They are very reactive. A marble size piece of sodium can exclode when dropsed into water. Other metals are lithium, potassium, and ridium.

Front 29

Alkali earth metals

Back 29

fairly reactive though not quite as reactive as alkali metals. Calcium when dropped into watrer won'dt explode as sodium does. Other are magnesium, strontium, and barium.

Front 30

Halogens

Back 30

Very reactive non metals. Group 7A. Chlorine is the most familiar. Because of its reactivity it is often used in disenfecting. Other are bromine, iodinem and fluorine.

Front 31

Periodic Law

Back 31

When the elements are arranged in order of increasing relative mass, certain sets of properties recur periodically.

Front 32

How is the periodic table organized?

Back 32

It is organized by listing the elements in order of increasing atomic number.

Front 33

What is a family or group of elements?

Back 33

Each column within the main group elements in the periodic table is labeled as a family or group of elements. The elements within a group usually have similar chemical properties.

Front 34

Give the group number for:
Alkali metals
Alkaline earth metals
Halogens
Noble Gases

Back 34

Alkali metals-Group 1A
Lakaline Earth Metals-Group 2A
Halogens-Group 7A
Noble Gases-Group 8A

Front 35

What is an ion?

Back 35

An ion is an atom or group of atoms that has lost or gained electrons and has become charged.

Front 36

What is an anion? What is a cation?

Back 36

anions are ions that have negative charges. Cation are ions with positive charges.

Front 37

Locate each of the following on the periodic table and list teh charge of the ions they tend to form:
Group 1A
Group 2A
Group 3A
Group 6A
Group 7A

Back 37

Group 1= +1
Group 2= +2
Group 3= +3
Group 6= -1
Group 7= -2

Front 38

What are isotopes?

Back 38

Atoms with the same number of protons but different numbers of neutrons are isotopes.

Front 39

What is the percent natural abundance of isotopes?

Back 39

The percent natural abundance of isotopes is the relative amount of each different isotope in a naturally occurring sample of a given element.

Front 40

What is the mass number of an isotope?

Back 40

The mass number is the number of protons + number of neutrons.

Front 41

What notations are commonly used to specity isotopes? What do each of the numbers in these symbols mean?

Back 41

Isotopes are A/Z X. X represents the chemical symbol. A represents the mass number and Z represents the atomic number.

Front 42

What is the atmoic mass of an element?

Back 42

The atomic mass of each element is listed in the periodic table directly beneath the element's symbo. It represents the average mass of the atoms that compose that element.

Front 43

When were the Bohr model and the quantum mechanical model for the atom developed? What is their purpose?

Back 43

Both the Bohr model and the quantum mechanical model were developed in the early 1900s. These models serve to explain how electrons are arranged within the atomic structure and how the electrons affect the chemical and physical properties of each element.

Front 44

What is light?

Back 44

Light is a form of electromagnetic radiation, a type of energy that travels through space at a constant speed of 3.0x10^8 m/s,

Front 45

Energy carried per photon is greater when the wavelength is?

Back 45

Shorter

Front 46

When the wavelength is long energy level is?

Back 46

low.

Front 47

What produces gamma rays?

Back 47

are produced by the stars, sun, and by certain unstable atomic nuclei on Earth.

Front 48

Excessive exposure to gamma rays and xrays should be avoided because:

Back 48

xrays cary energy to damage biological molecules. This increases cancer risk.

Front 49

Why should excess exposure to ultraviolet light be avoided?

Back 49

It increases the risk of skin cancer and causes premature wrinkling of the skin.

Front 50

What objects emit infarred light? What technology exploits this?

Back 50

All warm objects, including human bodies emit infared light. Infarred sensors are often used in night vision technology to "see" in the dark.

Front 51

Why do microwave ovens heat food but seldom heat the dish the food is on?

Back 51

Infarred light is efficiently absorbed by water and can therefore heat substances that contain water. For this reason substances that contain water, such as food, are warmed in a microwave, but substances that don't such as the plate don't.

Front 52

What type of electromagnetic radiation is used in communications devices such as celluar phones?

Back 52

radio waves are used.

Front 53

Describe the Bohr model for the hydrogen atom.

Back 53

The Bohr model is a representation for the atom in which electrons travel around the nucleus in circular orbits with a fixed energy at specific fixed distances from the nucleus.

Front 54

What is an emission spectrum? Use the Bohr model

Back 54

An emission spectrum A white light spectrum is continuous with some radiation emitted at every wavelength. The emission spectrum of an individual element, however, includes only certain specific wavelengths. The different wavelengths appear as lines because the light from the source passes through a slit before entering the prism.) Each element produces its own unique and distinctive emission sepectrum. The Bohr model tries to explain this by saying electrons travel around the nucleus in circular orbits that are similar to planetary orbits around the sun however, unlike the sun, electrons can only orbit at specific fixed distances from the nucleus.

Front 55

Explain the difference between a Bohr orbit and a quantum mechanical orbital.

Back 55

The Bohr orbit describes the path of an electron as an orbit or trajectory (a specified path). A quantum mechanical orbital describes the path of an electron using a probability map.

Front 56

What is the difference between the ground state of an atom and an excited state of an atom?

Back 56

Ground state is when an atom is at it's lowest energy tate. An atom that is excited is iin a higher energy orbital.

Front 57

Explain how the motion of an electron is different from the motion of a baseball. What is a probability map?

Back 57

The e- has particle duality which means the path of an electron is not predictable. The motion of a baseball is predictable. A probability map shows a statistical, reproductive pattern of where the electron is located.

Front 58

Explain why quantum mechanical orbitals have "fuzzy" boundaries.

Back 58

We just find where the most electrons will be found at any given moment in time. IT's not that we can pinpoint exactly where the atom is at any given time. We just know it will be somewhere within this possible area.

Front 59

List the 4 possible subshells in the quantum mechanical model, the number of orbitals in each subshell, and the maximum number of electrons that can be contained in each subshell.

Back 59

The subshells are s (1 orbital which contains 2 electrons), p (3 orbitals which contain a naximum of 6 electrons), d (5 orbitals, maximum of 10 electrons), f (7 orbitals and a max of 14 electrons).

Front 60

What is the Palui exclusion principle? Why is that important when writing electron configurations?

Back 60

The Pauli exclusion principle states that orbitals may hold no more than two electrons with opposing spin, and when 3 electrons are present in a single orbital, they must have opposite spins. When writing electron configurations, the principle means that no box can have more than 2 arrows, and the arrows will point in opposite directions.

Front 61

What is Hund's rule? Why is it important when writing orbital diagrams?

Back 61

Hunds rule states that when filling orbitals of equal energy, electrons fill them singly first, with parallel spins. This means orbitals fill with single electrons before they fill with paired electrons.

Front 62

Within an electron configuration what to symbols such as [Ne] and [kr] represent?

Back 62

They reprensent the noble gas core.

Front 63

Explain the difference between valance electrons and core electrons.

Back 63

Valance electrons are the electrons in the outermost principal shell (the principle shell with the highest quantum number, n). Core electrons are electrons that are not in the outermost principle shell.

Front 64

Give some examples of the explanatory power of the quantum mechanical model.

Back 64

The chemical properties of elements are largely determined by the number of valance electrons they contain. Elements with electron configurations closest to the noble gases are the most reactive because they can obtain noble gas core by losing or gaining small numbers of electrons.

Front 65

Explain why Group 1 elements tend to form 1+ ions ang Group 7 tend to form 1- ions.

Back 65

They want to do that because Group ones tend to want to lose one and have their outer shell be full. Group 7 want to gain one and have their outer shell be full and obtain a noble gas configuration.

Front 66

Explain the periodic trends in each of the following
Atomic size
Ionization energy
Atomic size
Metallic character

Back 66

As you moce to the right across a period or a row in the periodic table atomic size decreases. And as you nmove down it increases. This is due to adding outer energy rings.
Ionization energy As you move across the period ionization energy increases. When you move down ionization energy decreases. Because as an atom gets smaller it's difficult for it to hold electrons.
Metallic Character: as you move across metalliuc character decreases. As you move down it increases. This makes electrons more likelyu to be lost in chemical reactions

Front 67

Atom

Back 67

The simplest form of an element

Front 68

element

Back 68

A substance that cannot be divided.

Front 69

compounds

Back 69

two or more differnet atoms combined

Front 70

molecule

Back 70

2 or more atoms combined

Front 71

S is an atom and an element.
S2 is an element and a molecule
SO2 is a molecule and a compound

Back 71

ok

Front 72

what was the earliest concept people had of elements?

Back 72

Water wind fire, earth.

Front 73

Bohr models

Back 73

There are Newtonian models because we look at laws according to newton we give it a planitary orbit. Then we look at quantom modesl because they don't orbit at fixed distances. Then we have clouds of electrons and we talk about the possibility of finding the atom in the cloud,