Sycamore High Physical Science - Chapter 4

Front 1

Dalton's Atomic Theory

Back 1

Dalton proposed that all matter is made up of individual particles called atoms, which cannot be divided.

1. All elements are composed of atoms

2. All atoms of the same element have the same mass, and atom of different elements have different masses.

3. Compounds contain atoms of more than one element.

4. In a particular compound, atoms of different elements always combine in the same way.

Front 2

Thompson's Model of the Atom

Back 2

Thompson conducted experiments which provided evidence that atoms are made of even smaller particles. He hypothesized that negative charges were evenly scattered throughout an atom filled with a positively charged mass of matter.

Front 3

Rutherford's Atomic Theory

Back 3

According to the Rutherford model, all an atom's positive charge is concentrated in it's nucleus.

Front 4

Subatomic Particles

Back 4

Subatomic particles include protons, electrons, and neutrons. Protons, electrons, and neutrons can be distinguished by mass, charge, and location in an atom.

Front 5

Proton

Back 5

A proton is a positively charged subatomic particle that is found in the nucleus of an atom. Each proton is assigned a charge of 1+.

Front 6

Electrons

Back 6

An electron is a negatively charged subatomic particle that is found in the space outside the nucleus. Each electron has a charge of 1-.

Front 7

Neutrons

Back 7

A neutral subatomic particle that is found in the nucleus of an atom. It has a mass almost exactly to that of a proton.

Front 8

Atomic Number

Back 8

The atoms of a given element always have the same number of protons. The atomic number of an element equals the number of protons in an atom of that element. Since hydrogen (H) has one proton it is assigned the atomic number 1.

Front 9

Mass Number

Back 9

The mass number of an atom is the sum of the protons and neutrons in the nucleus of an atom.

Number of Neutrons = Mass number - Atomic Number

Front 10

Isotopes

Back 10

Isotopes are atoms of the same element that have different numbers of neutrons and different mass numbers. Isotopes of an element have the same atomic number but different mass numbers because they have different numbers of neutrons.

Front 11

Bohr's Model of the Atom

Back 11

Bohr's model of the atom focuses on the placement of electrons. In this model, electrons move with constant speed in fixed orbits around the nucleus, like planets around a sun. The possible energies that an electron have are called energy levels. An electron in an atom can move from one energy level to another when the atom gains or loses energy.

Front 12

Electron Cloud Model

Back 12

An electron cloud is a visual model of the most likely locations where the probability of finding an electron is high. Scientists use the electron cloud model to describe the possible locations of electrons around the nucleus. The electron cloud represents all the orbitals of the atom.

Front 13

Orbital

Back 13

An orbital is a region of space around the nucleus where an electron is likely to be found.

Front 14

Electron Configuration

Back 14

An electron configuration is the arrangement of electrons in the orbitals of an atom. The most stable electron configuration is the one in which the electrons are in orbitals with the lowest possible energies. When all the electrons in an atom have the lowest possible energies, the atoms is said to be in its ground state.