Atomic structure and the periodic table

Question 1

Atoms, elements and compounds

What is an atom?

Answer 1

The smallest part of an element that can exist

Question 2

Atoms, elements and compounds

What is an element?

Answer 2

A substance of only one type of atom

Question 3

Atoms, elements and compounds

What is a compound?

Answer 3

Two or more elements combined chemically in fixed proportions which can be represented by formulae

Question 4

Mixtures

What is a mixture?

Answer 4

Two or more elements or compounds not chemically bonded combined together

Question 5

Mixtures

Name the ways through which mixtures can be seperated.

Answer 5

• Filtration
• Crystallisation
• Simple and fractional distilliation
• Chromatography

Question 6

Mixtures

Explain simple distilliation

Answer 6

Simple distilliation is used to separate liquid from a solution - the liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid. Contrary to the evaporation, we get to keep the liquid.

Question 7

Mixtures

Explain crystallisation

Answer 7

Evaporation separates a solid dissolved in a solvent from a solvent. The solution is heated until all the solvent is evaporated.
Crystallisations is similar, but we only remove some of the solvent by evaporation to form a saturated solution. Then we cool it down. As we do it, the solid begins to crystallise, as it becomes less soluble at lower temperatures

Question 8

Mixtures

Explain factional distillation

Answer 8

Fractional distillation is a technique for separation of a mixture of liquids. It works when liquids have different boiling points.
The apparatus is similar to the one of simple distillation apparatus, with the addition fractionating column placed on top of the heated flask.This fractionating column contains glass beads. It helps to separate the compounds, In industry, mixtures are repeatedly condensed and vapourised. The colomn is hot at the bottom and cold at the top. The liquids will condense at different heights of the column

Question 9

Mixtures

Describe filtration

Answer 9

Filtration is used to separate an insoluble solid is suspended in a liquid. The insoluble solid (called a residue) gets caught in the filter paper, becuase the particles are too big to fit through the holes in the paper. The filtrate in the substance that comes through the filter paper. Apparatus: filter paper + funnel

Question 10

Mixtures

Describe chromotography

Answer 10

Chromotography is used to separate a mixture of substances dissolved in a solvent.
In paper chromotography, we place a piece of paper with a spot containing a mixture in a beaker with some solvent. The bottom of the paper has to be in contact with the solvent. The solvent level will slowly start to rise, thus separating the spot (mixture) into few spots (components)

Question 11

The development of the model of the atom

Describe John Dalton’s (billard ball) model

Answer 11

A tiny sphere that is indivisable ; the first ever model of the atom

Question 12

The development of the model of the atom

Describe JJ Thomsons ‘Plum pudding model’

Answer 12

A small ball of positive charge with negative electrons embedded throughout

Question 13

The development of the model of the atom

Describe Ernest Ruthfords model

Answer 13

A positive nucleus surrounded by negative electrons orbitting on energy shells

Question 14

The development of the model of the atom

Describe Rutherford’s alpha scattering experiment and it’s results

Answer 14

Rutherford directed a beam of alpha particles at a very thin gold leaf in a vacuum.
It was thought that all the particles would pass straight through. However, the results were:
- most alpha paricles did go straight through
- a smaal number of alpha particles were deflected by large angles, yet some came straight back out

Question 15

The development of the model of the atom

Describe Niels Bohr’s model

Answer 15

Bohr adapted the nuclear model by suggesting that the electrons orbit at specific distances

Question 16

The development of the model of the atom

Describe the current model

Answer 16

James Chadwick provided evidence for the existence of neutrons inside the nucleus. The current model consists of protons and neutrons in the nucleus and electrons orbitting on energy shells at specific distances.

Question 17

Relative electrical charges of subatomic particles

State the charges of the subatomic particles

Answer 17

• Proton - +1
• Neutron - 0
• Electron - -1

Question 18

Relative electrical charges fo subatomic particles

Why do atoms have no overall charge?

Answer 18

Atoms have the same number of protons as electrons. The charges cancel each other out.

Question 19

Size and mass of atoms

State the relative mass of atoms

Answer 19

• Protons - 1
• Neutrons - 1
• Electrons - 1/2000

Question 20

Size and mass of atoms

What is the radius of an atom?

Answer 20

0.1nm

Question 21

Size and mass of atoms

Whats the radius of the nucleus?

Answer 21

1 x 10^14

Question 22

Relative atomic mass

How do we calculate the relative atomic mass?

Answer 22

total mass of atoms / total number of atoms

Question 23

Electronic structure

Give the electronic configurations of He (2), Be (4), F (9), Na (11) and Ca (20)

Answer 23

2
2,2
2,7
2,8,1
2,8,8,2

Question 24

Electronic structure

What are ions?

Answer 24

Ions are an atom that has lost or gained electrons

Question 25

# Metals and non-metals Compare the properties of metals and non-metals

Answer 25

Metals - high m.p and b.p - conducts heat and electricity - shiny - malleable - - very dense - basic oxides Non-metals - low m.p and b.p - cant conduct - dull - brittle - not very dense - acidic oxides

Question 26

# Metals and non-metals Why can metals conduct electricity?

Answer 26

Metals have delocalised electrons that can move through the solution and carry a charge+

Question 27

# The periodic table How are elements grouped in the periodic table?

Answer 27

Elements in the same group have similar properties, and have the same number of outer shell elecrons. Elements in the same periods have the same number of shells

Question 28

# Development of the periodic table How did early scientists try to classify elements?

Answer 28

By arranging them in order of atomic weight. Early periodic tables were often incomplete, since many elements were unknown

Question 29

# Development of the periodic table How did Döbereiner arrange the elements?

Answer 29

Groups of 3 (triads) with similar properties

Question 30

# Development of the periodic table How did Newlands arrange the elements?

Answer 30

Groups of 8 (law of octaves) and stated that the element 8 places in front of it had similar properties

Question 31

# Development of the periodic table Who was Dmitri Mendeleev and how did he arrange the elements?

Answer 31

Dmitri Mendeleev was a Russian scientist, who arranged the elements in order of increasing atomic weight. He also took into account the properties of the elements and their compounds. This meant that his table: - had gaps in it for undiscovered elements - showed elements with similar chemical properties lined up in groups

Question 32

# Group 0 What are group 0 elements commonly known as?

Answer 32

Noble gases

Question 33

# Group 0 What is the trend going down group 0?

Answer 33

- The atoms become larger - The intermolecular forces between the atoms become stronger - More energy is needed to overcome these - The boiling points increase

Question 34

# Group 0 Why are the noble gases unreactive?

Answer 34

When elements react, their atoms complete their outer sheel by losing, gaining or sharing electrons. Group 0 elements already have a full outer shell and do not need to react.

Question 35

# Group 1 What are group 1 elements commonly known as?

Answer 35

Alkali metals

Question 36

# Group 1 What is the trend going down group 1?

Answer 36

- The atoms become larger - The outer electron becomes further away from the nucleus - The force of attraction decreases between the outer electron and the nucleus - The outer electron is lost more easily So, they get more reactive

Question 37

# Group 7 What are group 7 elements commonly known as?

Answer 37

Halogens

Question 38

# Group 7 What is the trend going down group 7?

Answer 38

- The atoms become larger - The outer shell becomes further away from the nucleus - The force of attraction decreases - An outer electron is gained less easily So, they become less reactive

Question 39

# Transition metals vs Group 1 elements Compare the physical properties of alkali metals and transition metals

Answer 39

Alkali metals - soft - low density - low m.p/b.p Transition metals - hard and strong - high density - high m.p/b.p

Question 40

# Transition metals vs Group 1 elements Compare the chemical properties of alkali metals and transition metals

Answer 40

Alkali metals - white/colourless compounds - reactive - react quickly with water - form +1 ions - not used as catalysts Transition metals - coloured compounds - not very reactive - react slowly with water - form ions with different charges - used as catalysts

Question 41

# Typical properties of transition metals What are the typical properties of transition metals?

Answer 41

- much harder and stronger - much less reactive - higher melting points These are all the general properties of metals