Sub-Ato

mic

Parti

cles

BLUE – HIGHLIGHT IT

RED – WRITE IT

1. The AtomA. Smallest whole part of matter.B. Contains 3 sub-particles:

1. Proton2. Neutron3. Electron

2. The Proton

C. If the number of protons in an element ever changes, the element has changed!

A. Each element is determined by its number of protons.

B. # OF PROTONS= ATOMIC #

1. The periodic table is arranged by increasing atomic number.

2. The PROTON D. Discovered in 1909.E. Located in the Nucleus.F. Positive charge.G. Held together by the

Strong Nuclear Force.1. Like repels like, so the force

needed to hold protons tightly packed is incredible.

2. A nuclear explosion breaks that bond and releases a massive amount of energy.

The NEUTRONA. The number of neutrons is determined by:

Atomic mass (rounded) – atomic number= NeutronsB. Number of neutrons can change!

1. Isotope: atoms of an element that have different numbers of neutrons.

C. Atomic Mass Number is the average of the masses of the isotopes for an element.

3. The NEUTROND. Discovered in 1931.E. Located in the nucleus.F. No charge.G. Held together by the

strong nuclear force.

4. The ELECTRONA. Negative charge.B. Almost no mass.C. In an element’s NATURAL state, the # of protons &

electrons are equal, neutralizing the atom’s charge.

THEREFORE, ATOMIC NUMBERIS ALSO EQUAL TO THE NUMBER OF ELECTRONS

4. The ELECTRON

D. Discovered in 1897.E. Located in Electron Cloud,

OUTSIDE the nucleus.F. Electron orbits:

1. 1st orbit: 2 electrons2. 2nd, 3rd, 4th orbits: 8 electrons

5. Valence Electrons

A. Electrons located in the outermost level of the cloud.

B. These electrons move from atom to atom during chemical reactions to form bonds.

1. Each atom is trying to fill its outermost level and will take in or lose electrons accordingly.

2. Atoms closer to the maximum number react more violently, since it’s very easy to gain or lose only 1 or 2 electrons.

3. Atoms at the maximum are stable & will not react (noble gases).

C. When the electrons move, IONS are formed.

1. Ions are elements with a charge.2. Sodium loses an electron, becoming +1.3. Chlorine gains an electron, becoming -1.