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Chapter 4

Atoms: Building Blocks of Matter

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Section 4-1

Structure of the Atom

+Structure of the Atom

Subatomic particles make up atoms.

3 main Particles.1. Protons

2. Neutrons

3. Electrons

+Protons

Positively charged particle.

Found in the nucleus.

Has the mass of 1 atomic mass unit. (very small)

It takes 600,000,000,000,000,000,000,000 protons to make 1 gram.

+Neutrons

Electrically neutral.

Found in the nucleus.

Mass of 1 atomic mass unit (amu).

+Protons and Neutrons

Found in the nucleus.

Both particles are at the center of the atom.

Extremely small.

Make up 99.9% of the mass of the atom.

Positively charged.

Size of a bee in a football stadium.

+Electrons

Negatively charged particle.

Found outside of the nucleus in the electron cloud.

Region where there is the most likely hood of finding an electron. The probable location of an electron in an electron cloud

will depend on how much energy the electron has.

+Electrons

Mass of 11836 amu.

Remember the shells or clouds are in energy levels. Lowest levels is closest to the nucleus. Highest is farthest away from the nucleus.

+Energy Levels

Energy levels can only hold a limited number of electrons. 1st- 2 electrons max 2nd- 8 electrons max 3rd- 18 electrons max 4th- 32 electrons max

The chemical properties of elements depend on how the electrons are arranged in the atom.

+Energy Levels

Each level has a specific Energy and if an electron loses or gains Energy it can move to different Energy levels.

When this happens, they give off light (it jumps up when it gains and down when it loses. The energy is light.)

Periodic Table

A. Atomic Number

B. Chemical Symbol

C. Name of the Element

D. Atomic Mass

11

NaSodium

22.990

A

B

C

D

+Periodic Table

The atomic number- the number of protons in the atom. It is the number of protons in an atom that

makes it the element it is.

Isotopes are atoms of the same element with the same number of protons, but different number of neutrons. Ex: Carbon always has 6 protons. Carbon 12 – 6 protons and 6 neutrons. Carbon 14- 6 protons and 8 neutrons.

+Periodic Table

Mass number or atomic mass- Equals the number of protons + neutrons. # Neutrons = mass # - atomic number. Atomic mass is the average mass of all

isotopes in nature on the periodic table. Because atoms are neutral, # protons = #

electrons. Atomic number = # protons = # electrons.