4) Periodicity

Question 1

Periodicity

Answer 1

Regular recurrence of properties

Question 2

Periodic law

Answer 2

(Mendelev 1869) properties of elements vary periodically with atomic numbers

Question 3

Melting/boiling point trends

Answer 3

• Boiling point for noble gases and halogens increase going down the group
• Other groups: no consistent trends in melting and boiling points down a group: the elements are all just solids

Question 4

Atomic radius trends

Answer 4

Decreases from left to right across any period of the periodic table

Question 5

Ion

Answer 5

An atom loses or gains an electron, and becomes electrically charged because the number of protons and electrons are no longer in balance

Question 6

Ionisation

Answer 6

An atom or molecule has a negative or positive charge by gaining or losing electrons

Question 7

Ionisation energy

Answer 7

Energy required to remove an electron from an atom

Question 8

First vs second ionisation energy

Answer 8

• First ionisation energy: energy needed to remove the first electron from a neutral atom
• Second ionisation energy: energy required to remove a second electron from a 1+ ion (meaning the atom has already lost one electron)

(this continues)

Question 9

Ionisation energy trends

Answer 9

Going across periods, the first ionisation energy increases: in moving left to right, there is less tendency to lose electrons

Going down groups, ionisation energy decreases: in going down any group, electrons are lost more easily

Question 10

Relationship between atomic radius and first ionisation energy

Answer 10

As atomic radius increases, first ionisation energy decreases

Question 11

Electronegativity of an element

Answer 11

Element’s tendency to attract electrons when forming a chemical bond

Higher electronegativity = stronger attraction of atoms for bonding electrons

Question 12

What is the electronegativity for noble gases

Answer 12

0

Question 13

Electronegativity trends

Answer 13

Increases left to right across a period, decreases from top to bottom down a group

Question 14

Metallic character trends

Answer 14

Decreases across periods left to right, increases down groups (groups 14/15 especially)

Question 15

What elements (groups) react with water

Answer 15

Group 1: becomes more vigorous moving down
Group 2: beryllium does not react, from then reactions grow but not like group 1

Always metals - form hydrogen gas and hydroxide

Question 16

Relationship between atomic radius and element reactivity with water

Answer 16

• Larger the atomic radius = more reactive metal
• Weaker electrostatic attraction leads = larger atom and also makes it easier for the atom to lose an 1 or 2 outermost electron to become an ion