part 1 - module 2

Question 1

trends in periodic table - Halogens, group 17

Answer 1

• As you go down the group: melting points ↑ , reactivity ↓
  *

all the halogens can exist as pairs of atoms called diatomic molecul

further explanation: https://www.youtube.com/watch?v=HT1zAPQIBAQ

Question 2

Trends in periodic table - Noble gases

Answer 2

• as you go down group: boiling point ↑

noble gases are stable, and exist as single atoms. they are non-flammable

Question 3

representative elements

on periodic table

Answer 3

are the elements in group 1 and 2, and last 6 groups on the right.

avoiding transition metals

group number in periodic table = number of valence electrons (representative elements only)

Question 4

Non-representative elements/transition elements

Answer 4

elements occupying central block of periodic table.

some trends: they have electrons in d subshells, but most do not have completely fileld d subshells..

Question 5

cation

Answer 5

a cation has lost an electron and THUS has a positive charge

like the “t” in “cation” looks like a plus.

finding electronic configuration of cations:
refer to page 18 of qs chem part 1 module 2

Question 6

anion

Answer 6

an anion is an atom that has gained an electrons and THUS has a negative charge.

finding electronic configurtion of anions:
place the additional electron in the next available subshell.
eg.
O = [He] 2s^2 2p^4
turns into →
O = [He] 2s^2 2p^6

Question 7

isoelectronic

Answer 7

atoms and ions with the same electron configuration is known as isoelectronic.

eg. fluorine gains 1 electron.
Oxygen gains two electrons.
both have sam

Question 8

electron affinity

affinity definition: the degree to which a substance tends to combine with another.

Answer 8

the electron affinity of an atom/molecule is defined as the amount of energy released when an electron is added to a neutral atom/molecule in the gaseous state to form a negative iron.

to simplify, when an atom wants an electron, it will ‘pay’ for the electron by giving energy out.

refer qs pg 19, part 1.

atom wants an electron = eletron affinity will have a high POSITIVE value.

atom does not want an electron = we may need to add energy to the atom to force it to produce an ion = atom will then have a NEGATIVE electron affinity.

Question 9

ionisation energy

Answer 9

the minimum energy required to remove an electron from a gaseous atom in its ground state.

eg. Lithium, [He] 2s^1 = remove single electron in the 2s subshell, making [He].

requires energy to remove electron, working against the attraction.

unlike electron affinity values, ionisation energy values are always positive.