Atomic + Lewis Structures

Question 1

What are isotopes?

Examples of naturally occurring isotopes

Answer 1

atoms of the same element with the same atomic number (protons) but different atomic mass (neutrons)

same protons but different neutrons
hydrogen - 1, 2, 3
carbon - 12, 13, 14

Question 2

What is Pauli’s exclusion principle? What is Hund’s rule?

Answer 2

Pauli’s Exclusion Principle
- maximum of 2 electrons in each orbital of opposite spin (must be opposite spin)

Hund’s Rule
- an electron will occupy an empty degenerate orbital before it will pair up

Question 3

What does degenerate orbital mean?

Answer 3

the orbitals have the same energy orbital = equal

Question 4

What are valence electrons? What is a valence number?

Answer 4

valence electrons - electrons in the outermost shell

valence number - the same as the group number/ represents the number of electrons in the last shell

Question 5

How does the energy of orbital change depending on distance between it and the nucleus?

Answer 5

the closer the orbital is to the nucleus, the lower its energy

Question 6

What do lewis symbols show?

Answer 6

lewis symbols show the outermost electrons of elements

- appear as dots next to the element symbol

Question 7

What is the octet rule?

Answer 7

atoms tend to lose or gain or share electrons until they’re surrounded by 8 electrons

Question 8

What is ionic bonding?

Answer 8

electrostatic forces between ions

• usually a metal cation and non-metal anion
• compounds created are highyl crystalline and have high melting points
• used to form noble gas electronic configuration = octet

can act over long distance and are strong

Question 9

What are covalent bonds?

Answer 9

bond results from sharing electrons between 2 atoms = each carries two electrons

• usually non-metals
• results in molecules = gases, liquids or low melting point solids

Question 10

What are exceptions to the octet rule?

Answer 10

molecules with an odd number of electrons - free radicals

other natural radicals which do not obey lewis structures - oxygen

molecules in which an atom has more than an octet

molecules in which an atom has less than an octet

Question 11

How are molecules with less than an octet an exception to the rule?

Answer 11

Lewis acid - accepts a pair of electrons to form an octet
Lewis base - donates a pair of electrons to form a stable octet

Lewis acid + Lewis Base = Salt + Water

Question 12

How are molecules with more than an octet an exception to the rule?

Answer 12

elements in period 3 have more than an octet as they have 9 valence orbitals

• have empty s, p and d orbitals that can be used in bonding
• can have more than 8 electrons around the central period 3 element = S, P

the large the central atom, the more atoms that can be bound to it

Question 13

What are formal charges?

Answer 13

formal charges on an element is

valence electrons (group number) - number electrons on the atom in the lewis structure

Question 14

What are radicals/free radicals?

Answer 14

atom, molecule or ion with an unpaired electrons

• odd number of electrons
• uncharged species
• unstable
• reactive