Natural Science Chemistry Review

Front 1

The smallest part an element can be broken into while retaining all the properties of that element.

Back 1

Atom

Front 2

What are the 3 particle that make an atom?

Back 2

Proton
Electron
Neutron

Front 3

What is atomic weight?

Back 3

The total umber of particles in the nucleus

Front 4

What is an isotope?

Back 4

Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes.

Front 5

What is an atomic number?

Back 5

The number of protons in the nucleus determines the atomic number.

Front 6

Where is the atomic number written?

Back 6

The atomic number is written on the lower-right or the lower-left of the chemical symbol.

Front 7

Are atoms electrically neutral?

Back 7

Yes! For every proton there is an electron so the number of positive (+) charges = the number of negative (-) charges leaving the atom in aneutral electrical state.

Front 8

Where are electrons located?

Back 8

Electrons are located outside the nucleus in the rings, orbits, shells, or levels (all mean the same thing).

Front 9

How many levels can an atom have?

Back 9

Up to 7, but only if there are electrons present in that level.

Front 10

How many elements are there?

Back 10

There are 104 recognized elements. 92 are natural, 12 are synthetic.

Front 11

What is the chemical symbol for aluminum?

Back 11

Al

Front 12

What is the chemical symbol for Calcium?

Back 12

Ca

Front 13

What is the chemical symbol for Carbon?

Back 13

C

Front 14

What is the chemical symbol for Copper?

Back 14

Cu

Front 15

What is the chemical symbol for Iron?

Back 15

Fe

Front 16

What is the chemical symbol for Lead?

Back 16

Pb

Front 17

What is the chemical symbol for Magnesium?

Back 17

Mg

Front 18

What is the chemical symbol for Phosphorus?

Back 18

P

Front 19

What is the chemical symbol for Potassium?

Back 19

K

Front 20

What is the chemical symbol for Silicon?

Back 20

Si

Front 21

What is the chemical symbol for Sodium?

Back 21

Na

Front 22

What is the chemical symbol for Sulfur?

Back 22

S

Front 23

What is the chemical symbol for Uranium?

Back 23

U

Front 24

What is the chemical symbol for Zinc?

Back 24

Zn

Front 25

What is the chemical symbol for Mercury?

Back 25

Hg

Front 26

What is the chemical symbol for Bromine?

Back 26

Br

Front 27

What is the chemical symbol for Nitrogen?

Back 27

N(2)

Front 28

What is the chemical symbol for Oxygen?

Back 28

O(2)

Front 29

What is the chemical symbol for Hydrogen?

Back 29

H(2)

Front 30

What is the chemical symbol for Chlorine?

Back 30

Cl(2)

Front 31

What is a diatomic molecule?

Back 31

A diatomic molecule is when 2 atoms form 1 molecule. The diatomic gasses are (O"2", H"2", N"2", and Cl"2")

Front 32

A ________ __________ is the process by which elements and compounds split or combine o form different elements and compounds.

Back 32

chemical reaction

Front 33

(OH) with or without brackets usually denotes what?

Back 33

a base

Front 34

When H begins a chemical equation it usually denotes what?

Back 34

an acid

Front 35

What is the Law of Conservation of Matter?

Back 35

Matter can neither be created or destroyed.

Front 36

How should this formula be written?

NaCl + F(2) ---- NaF +Cl(2)

(the number in parenthesis is a subscript)

Back 36

2NaCl + F(2) --- 2NaF +Cl(2)

(this way it complies with the law of conservation of matter)

Front 37

How should this formula be written?

H(2) + O(2) --- H(2)O

(the number in parenthesis is a subscript)

Back 37

2H(2) + O(2) --- 2H(2)O

(this way it complies with the law of conservation of matter)

Front 38

When matter combines chemically it is a ________ ____. It shares electrons.

Back 38

covalent bond

Front 39

Another kind of chemical bonding is the _____ ____. In this type of bonding the electrons are moved from one atom to another.

Back 39

ionic bond

Front 40

Why are oppositely charged ions attracted to each other?

Back 40

Because of electrostatic forces, which is the basis of the ionic bond.

Front 41

What are the 2 particles of energy?

Back 41

alpha and beta

Front 42

What does and alpha particle stand for?

Back 42

a-alpha particle = He(4/2) (a helium nucleus)

Front 43

What is a beta particle?

Back 43

beta particle = e- (from the decay of neutron)

Front 44

The ____-____ of a radioactive substance is the amount of time it takes for one-half of that substance to undergo decay.

Back 44

half-life

Front 45

If the half-life of U238 is 4.5 billion years and you had 1 pound 4.5 billion years ago, how much would exist now?

Back 45

Only 1/2 pound of U238 would exist now.

Front 46

A substance passed through 4 half-lives. How much of the original substance remains? How much has decayed?

Back 46

(1/2)n=(1/2)4=1/2 x 1/2 x 1/2 x 1/2 = 1/16

(only 1/16 of the original radioactive substance remains, and 15/16 has decayed)

Front 47

A radioactive substance has a half-life of 25 years and passes through 5 half-lives. How many years does it take to pass through 5 half-lives?

Back 47

25 years/1 half-life x 5 half lives = 125 years

Front 48

A radioactive substance has a half-life of 25 years and passes through 5 half-lives. How much of the original material remains?

Back 48

(1/2)n = (1/2)5 = 1/2 x 1/2 x 1/2 x 1/2 x 1/2 = 1/32

1/32 of the original substance remains.

Front 49

A radioactive substance has a half-life of 25 years and passes through 5 half-lives. How many years will it be before 99% of he original substance decays?

Back 49

(1/2)n=(1/2)2 = 1/4
(1/2)3 = 1/8
(1/2)4 = 1/16
(1/2)5 = 1/32
(1/2)6 = 1/64
(1/2)7 - 1/128

1/128 is closer to 1/100 (1/100 equals 1% of the original substance remaining or 99% decayed).

So, the substance must pass through close to seven half-lives.