Development of the periodic table

Question 1

Plum pudding model

Answer 1

Ball of positive charge
Negative electrons embedded into it
No shells
No nucleus
No protons

Question 2

Alpha scattering experiment

Answer 2

Take a piece of gold foil only a few atoms thick
Fire alpha particles (positive charge) at this sheet
Most passed through
Some was deflected
Some completely bounced back

Question 3

What did the alpha scattering experiment tell us?

Answer 3

Went straight through = atoms have empty space
Deflected = they must come close to a positive charge in the centre
Bounced back = positive centre has a great deal of mass and positively charged (nucleus)

Question 4

The nuclear model

Answer 4

Empty space with a positive nucleus where mass is concentrated
Electrons don’t orbit at specific distances

Question 5

Bohr’s model

Answer 5

Electrons orbit around the nucleus in specific distances in shells
Accepted because it agreed with other scientists results

Question 6

Discovery of protons and neutrons

Answer 6

What made up most of the nucleus
What made up the atom’s mass

Question 7

Isotopes

Answer 7

Atoms of the same element (same number of protons) with a different number of neutrons

Question 8

Relative atomic mass

Answer 8

Average of the mass numbers of different isotopes weighted based on its abundance

Question 9

Who discovers protons?

Answer 9

Rutherford

Question 10

Who discovered neutrons?

Answer 10

Chadwick

Question 11

Döberiner’s triads

Answer 11

Elements with similar properties occur in 3s
Started the question of arranging elements in a logical order

Question 12

Newland’s octaves

Answer 12

Arrange elements with increasing mass number
Every 8 elements have similar properties

Question 13

Problem with newland’s octaves?

Answer 13

Grouping by atomic weight means elements with different properties grouped together
Not taken seriously

Question 14

Mendeleev’s table

Answer 14

Arranged in increasing atomic weight
But also
switched order of some to fit properties into their groups
Left gaps for undiscovered elements

Question 15

Why was Mendeleev’s table accepted?

Answer 15

Predicted properties for the undiscovered elements correctly
Since they were discovered later

Question 16

How is the modern periodic table different?

Answer 16

Discovery of protons therefore the atomic number
So ordered by atomic number
And contains the noble gases

Question 17

What determines the reactivity?

Answer 17

Elements in the same group react similarly
Because they have the same number of electrons in its outer shell

Question 18

Radius of an atom

Answer 18

0.1nm
Or 1x10^-10 m

Question 19

Radius of the nucleus of an atom?

Answer 19

1/1000 the size of a radius of the atom
Or 1x10^-14m

Question 20

Group 0

Answer 20

Noble gases

Question 21

Group 0 properties

Answer 21

Very unreactive
Boiling points increase as you go down

Question 22

Why is group 0 unreactive?

Answer 22

Because they have a full outer shell of electrons

Question 23

Why do boiling points of noble gases increase going down?

Answer 23

Because the atoms get bigger going down
So they have stronger intermolecular forces due to having a shorter distance
So require more energy to overcome them

Question 24

Categories of metals

Answer 24

Group 1 and 2
Transition metals
Post transition metal

Question 25

Group 1 metals

Answer 25

Alkali metals that are in group 1 So have 1 electron in outer shell

Question 26

Group 1 physical properties

Answer 26

Very soft = cut with a knife Low density Low melting points

Question 27

Group 1 chemical properties

Answer 27

React rapidly with oxygen = metal oxide React rapidly with halogen React rapidly with water = alkali hydroxide and hydrogen

Question 28

Group 1 reaction with oxygen eg lithium

Answer 28

4Li + O₂ —> 2Li₂O Same for ALL group 1

Question 29

Group 1 reaction with a halogen eg lithium and chlorine

Answer 29

2Li + Cl₂ —> 2LiCl Same for ALL group 1 and halogens

Question 30

Group 1 reaction with water eg lithium

Answer 30

2Li + 2H₂O —> 2LiOH +H₂ Forms a metal hydroxide and hydrogen (effervescence)

Question 31

Why does group 1 reactivity increase going down?

Answer 31

In order to react group 1 metals must lose outer shell electron Going down means an increased number of internal shells Meaning less electrostatic attraction between outer electron and positive nucleus And greater distance So going down loses electrons easier = increased reactivity

Question 32

Transition metals physical properties

Answer 32

Hard and strong High melting point High density

Question 33

Transition metals chemical properties

Answer 33

Less reactive than group 1 Forms ions of different charges Forms coloured compounds Used as catalysts

Question 34

Group 7

Answer 34

Halogens Non metals Have 7 electrons in outer shell

Question 35

Boiling and melting point trends with halogens

Answer 35

Increase as you go down Meaning more energy required to melt and boil it

Question 36

Fluorine and chlorine physical properties

Answer 36

Gas at room temperature Since it’s boiling point to become a gas is very low

Question 37

Bromine physical property

Answer 37

Liquid at room temperature Because it’s boiling point to become a gas is above 20°c but it’s melting point is below that

Question 38

Iodine physical property

Answer 38

Solid at room temperature Because it’s melting and boiling point to become a liquid or a gas is above room temperature

Question 39

Halogens chemical properties

Answer 39

Bond with each other covalently to form simple molecule Forms covalent compounds with other non metal elements Forms a negative ion when reacted with a metal Reactivity decreases going down

Question 40

Why do halogens decrease in reactivity going down?

Answer 40

Because in order to react they must gain an electron Atoms increase in size going down the group Meaning more shielding due to internal shells And a greater distance between the positive nucleus + electron So less electrostatic attraction between them so less reactive going down