1. ATOMS REVIEW 2014 December Benchmark

2. AN ATOM IS CONSIDERED TO BE NEUTRAL IF IT HAS EQUAL PARTS OF ______________ AND _________________. An atom is considered to be neutral if it has equal parts of PROTONS and ELECTRONS.

3. WHICH SUBATOMIC PARTICLE IS USED TO IDENTIFY AN ELEMENT? PROTONS!! ATOMIC NUMBER = PROTONS = How you identify an element! This number INCREASES as you move across the period. Atomic Mass = PROTONS + NEUTRONS

4. PERIODS Direction on the Periodic Table Tells the number of SHELLS (or rings, or energy levels or orbitals) List the elements in period 3: Na, Mg, Al, Si, P, S, Cl, Ar

5. GROUPS Direction on the Periodic Table Tells the number of VALENCE ELECTRONS for all atoms in that column. Shows that elements have similar CHEMICAL and PHYSICAL properties. List the elements in group 3: B, Al, Ga, In, Tl

6. WHAT ON THE PERIODIC TABLE INCREASES AS YOU GO LEFT TO RIGHT? Atomic NumberYes Number of Subatomic Particles Yes Number of Valence Electrons Yes

7. WHAT ARE VALENCE ELECTRONS? Valence electrons are the electrons on the outermost shell of an atom. Valence electrons can be found by looking at the atom’s GROUP number. Valence electrons determine the CHEMICAL properties of an element.

8. WHERE CAN I FIND GROUP NUMBERS? Group numbers are located at the TOP of the COLUMN on the Periodic Table.

9. DIAGRAMS ON PERIODIC TABLE Label the diagram to the right. Atomic mass is equal to PROTONS + NEUTRONS. (Atomic Mass – ATOMIC NUMBER = Neutrons) Atomic Number (Protons) Chemical Symbol Chemical Name Atomic Mass

10. SUBATOMIC PARTICLES SUBATOMIC PARTICLE LOCATIONCHARGESIZE (MASS) Protons NucleusPositive (+)1 amu ElectronsElectron Cloud Negative (-)0 amu NeutronsNucleus Neutral (0)1 amu

11. SODIUM ATOM p = Protons (positive charge in nucleus) n= Neutrons (neutral charge in nucleus) Electrons are the black dots in the rings surrounding the nucleus The black dot in the outermost ring is a valence electron There is one valence electron, so the element is in group #1 There are 3 rings, so the element is in period #3