The Periodic Table

Question 1

How did Mendeleev organise the periodic table?

Answer 1

In order of atomic weight
Arranged them by properties (group 7 halogens, group 0 noble gases)
Left gaps

Question 2

Metal properties

Answer 2

Conduct electricity
High melting and boiling points
Left of staircase
Lose electrons

Non-metal properties opposite
Usually are gases or liquids at room temperature
Gain electrons

Question 3

Group 0

Answer 3

Noble gases
8 electrons in outer shell - stable
Unreactive
Difficult to combine with other elements

Question 4

Group 1 and 2

Answer 4

Reactive Metals
React vigorously with other elements and water
SoftN

Question 5

Transition Metals

Answer 5

Middle area
Not usually reactive
Reactivity series

Good conductors
Hard and strong
High densities
High melting points

Question 6

Alkali Metals

Answer 6

Group 1
At top = less reactive, high melting/boiling point (Li)
At bottom = most reactive, low melting/boiling point (Fr)

Reactive - stored in oi
1 electron in outer shell
Low density, soft, shiny
Low melting and boiling points

Reaction with water:
React with H2O form H2 gas
K burns with lilac flame
Soluble in water
Solution = colourless
Fizzes so exothermic reaction

Question 7

Halogens

Answer 7

Group 7 (7 electrons in outer shell)
At top = most reactive, low boiling/melting point
At bottom = least reactive, high boiling/melting point

Non-metals
Diatomic = share electron in their pairs, so both gain an electron (Cl2, F2, Br2)
Highly reactive -> only need to gain 1 electron
Gain 1 electron = -1 charged ions, OILRIG gains electron so is reduction

More reactive displaces less reactive element:
Br2 + 2NaI -> 2NaBr + I2
Iodine less reactive so is displaces
If it was Cl, no reaction, chlorine is more reactive

Question 8

Reactivity within groups (atoms and shells)

Answer 8

Go down groups → shells increase by one electron shell per period

Atoms get larger going down any group:

• Larger atoms lose electrons more easily going down group
• Larger atoms gain electrons less easily going down group

Question 9

Explaining trend in group 1

Answer 9

Reactivity decreases going down
Atoms get larger
1 electron (negative) in outer shell attracted less strongly to positive nucleus
Electrostatic attraction gets weaker
Outer electron shields inner shells, reducing attraction
Size of positive charge increases
Nuclear charge increases
Changes from Li to Li+ takes more energy than Na to Na+ because of reactivity

Question 10

Explaining trend in group 7

Answer 10

Reactivity decreases going down group 7:
Size of atom
Shielding effect
Nuclear chare

When react, gain electron = reduction