CHEM 120 WEEK 8 FINAL EXAM REVIEW | UPDATED 2025 | STUDY GUIDE

CHEM 120: WEEK 8 Final EXAM
1. Question: Know what is the atomic number, atomic mass, protons, neutrons &
electrons

Atomic number – is the number of protons in the nucleus of an atom of any
element
Atomic mass – is expressed in amu; is the wighted average
Protons – are positively charged particles in the nucleus
Neutron – are neutral, have no electrical charge
Electrons – are negatively charged particles in the nucleus
Atomic number = number of protons
Atomic number – (minus) atomic mass = neutrons

2. Question: Describe the shapes of molecules H2S, CBr4, & PCl3

, H2S – bent
• Number of bonded atoms: 2
• Number of lone pairs: 2
• Number of electron sets: 4
CBr4 – tetrahedral
• Number of bonded atoms: 4
• Number of lone pairs: 0
• Number of electron sets: 4
PCl3 – pyramidal
• Number of bonded atoms: 3