Module 3: Atomic Theory and Structure

Question 1

What is the law of definite composition?

Answer 1

A compound always contains 2 or more elements chemically combined in a definite proportion by mass

Question 2

What is the law of multiple proportions?

Answer 2

Atoms of 2 or more elements may combine in different ratios to produce more than one compound

Question 3

How to calculate the neutron?

Answer 3

Neutron = Mass number - Atomic number

Question 4

What is an isotope?

Answer 4

two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, different atomic mass but not in chemical properties

Question 5

What is the average atomic mass and how it is calculated?

Answer 5

The average atomic mass is calculated by multiplying the atomic mass of each isotope by its abundance in nature and adding the result. 
Isotopic mass (AMU)(abundance (in decimal points%) + (another amu)(abundance%)  = x amu

Question 6

What is an orbital?

Answer 6

orbital is a region in space around the nucleus where there is a high probability of finding a given electron.
(s, p, d, f)

Question 7

Describe principle energy levels

Answer 7

• Principal energy level of an electron refers to the shell or orbital in which the electron is located relative to the atom’s nucleus
• The energy of electrons is restricted to certain limits “quantized”.
• Represented by n (positive integer): the lowest is n=1, then n =2 ➡️ as n increases, the energy of electron increases, the electron is further away from the nucleus

Question 8

What are sublevels in the principle energy levels?

Answer 8

• Each principle energy levels is divided into sublevels
• 1st principle = 1 sublevel, 2nd principle =2 sublevels, 3rd principle = 3 sublevels
• Each sublevel contain spaces for electrons aka orbitals

Question 9

Explain Spin in relation to Pauli exclusion principle

Answer 9

• each electron is spinning on an axis like a globe

Pauli’s exclusion principle: electron can only spin in 2 directions ⬆️ ⬇️. Only 2 opposite spin can occupy one orbital

Question 10

Describe a summary of principle energy levels

Answer 10

n=1 1s
n=2 2s 2p 2p 2p
n=3 3s 3p3p3p 3d3d3d3d3d
n=4 4s 4p4p4p 4d4d4d4d4d 4f4f4f4f4f4f4f

1 orbitals = 2 electrons 
orbitals: (represented in lines) 
s= 1 
p=3
d=5
f=7

sublevels: "l"
s=0 
p=1
d=2
f=3 

orientation of the spin: “ms”
⬆️: +1/2
⬇️: - 1/2