TOPIC 1 - Atomic Structure + The Periodic Table

Describe the plum pudding model

a ball of positive charge; with negative electrons embedded

Differences between the plum pudding model and the model used today

• both contain electrons

• both are neutral overall

• PPM has no nucleus

• PPM has no proton or neutrons

• PPM has positive charge spread throughout the atom/ ball of +ve charge

• PPM - electrons are randomly place; today's - in energy levels/ shells

• PPM - mass spread throughout; today's - concentrated at centre

• PPM - no empty space; today's - mostly empty space

What are isotopes?

atoms with the same number of protons; with different numbers of neutrons

How could you predict how many outer-shell electrons an element has?

look at the group it is in the periodic table

Why are new elements and theories not accepted as soon as they are discovered?

time is needed for peer review

Describe how to obtain sodium chloride crystals from sodium chloride solution by crystallisation

heat the solution until it reaches crystallisation point; leave the solution to cool and crystallise

Why don't Group 8 elements form compounds?

they have a stable arrangement of electrons (full outer shell); so don't share or transfer electrons

How can you predict if an element reacts with metals?

If it towards the right of the periodic table -> non-metal; or in the same group as other non-metals/ elements that react with metals

Observations when a Group 2 metal reacts with HCL acid (Mg, Ba, Ca)

effervescence; the metal disappears; forms a colourless solution

Evidence to show rubidium is more reactive than Mg when reacting with HCL acid

brighter/ bigger flame; more vigorous bubbling; disappears more quickly;

Explain what happens when you go down Group 1

the elements increase in reacitvity; the outer shell electron is further from the nucleus; so less electrostatic attraction between the nucleus and outer electron; and there is more shielding with more energy levels; so the outer electron is more easily lost

Explain what happens when you go down Group 7

the elements decrease in reactivity; more electron shells/ energy levels so weaker electrostatic force; so harder to gain electron from other atoms to complete shell; also more electron shielding.

Explain what happens to the boiling points as you go down Group 7

the boiling points increase; the size of molecule increases; so the intermolecular forces increase in strength; so more energy is needed to overcome the intermolecular forces

What do the Group 1 metals react with water to give?

A hydroxide + hydrogen

What does an element consist of?

One type of atom

What is the difference between a mixture and a compound?

the atoms in a compound are chemically combined together in fixed proportions

If the length of a fine particle is 10x smaller than a coarse particles, what happens to its SA

V ratio?

Why did the discovery of gallium help Mendeleev's table be accepted?

gallium fitted in the gap he had left; its properties were predicted correctly by him

Why did Mendeleev not order the elements according to atomic number?

atomic number is the no. protons; protons weren't discovered until later

Why did Mendeleev reverse the order of some elements?

so their properties matched the rest of the group

What changes did Bohr make to the nuclear model?

Electrons orbit the nucleus; at specific distances from the nucleus

How did Chadwick's work support the understanding of isotopes?

Chadwick discovered neutrons (gave evidence to show their existence); this was necessary since isotopes have same no. protons, diff no. neutrons

Why do atoms not have an overall charge?

they have the same number of protons and electrons

What is mass number?

the no. of protons plus no. neutrons/ their sum

What is the size of an atom + the nucleus

atom = 1x10^-10 (0.1nm); nucleus = roughly 1x10^-14m

If a nucleus is presented as a ball with a radius 1cm, how big is the atom?

a sports arena radius 100m

How to separate water and sand mixture?

Filtration - funnel with filter paper into a beaker/ flask

Describe the process of distillation to remove water from pure salt

solution is heated; water evaporates; the vapour cools in the condenser; the vapour condenses into a liquid; the pure water collects in a beaker

How did evidence from the alpha scattering experiment led to changes in the nuclear model?

most alpha particles pass straight through the gold foil; so atom is mostly empty space w/ mass concentrated in the nucleus/ centre; some were deflected; so has a positively charged nucleus;

What is an alloy?

a mixture of metals

Why is an alloy harder than a pure metal?

The layers are distorted in the alloy so harder for the layers to slide over each other

Properties of Transition Metals (chem + phy)

Physical - high melting points; high densities; strong; hard
Chemical - low reactivity/ react slowly with water/ oxygen; used as catalysts; ions with different charges; form coloured compounds

Why do all the elements in Group have similar chemical properties?

they have the same number of outer shell electrons

Observations when Group 1 metal reacts with water

floats; effervescence; moves around; flame in the lower elements; melts into a ball

Properties of Group 1 metals (phy + chem)

Physical - low melting points; low densities; soft
Chemical - very reactive wih water + non-metals; not used as catalysts; white/ colourless compounds; only form +1 ion

What are pure substances in chemistry + pure substances in everyday life?

In chemistry - a single element/ compounds; in everyday life - a substances that has had nothing added to it

Why can't you have a boiling point of a single molecule?

boiling point is a bulk property

Why was Mendeleev's table more accepted than previous models?

M had predicted properties of missing elements; elements were discovered that filled the gaps; and properties had matched his predictions

Observations when sodium reacts with chlorine

flame; white solid forms; chlorine disappears(colour of gas fades)

Why is hydrogen chloride a gas at room temperature?

Hydrogen chloride is made of small molecules; so has weaker intermolecular forces; require little energy to overcome

What are the vertical and horizontal groups called in the periodic table

V- groups; H - periods

Compare Newlands' Law of Octaves table vs Mendeleev

• Both tables have more than one element in a box
• Both have similar elements in the same column
• Both are missing noble gases
• Both arrange elements in order of atomic element
• Newlands didn't leave gaps for undiscovered elements; Mendeleev did
• Newlands had more dissimilar elements in a column; Mendeleev did
  -  Mendeleeve left gaps + changed the order of some elements

Sodium + water reaction

melts; efferevesces; sodium floats; sodium moves

What colour are copper ions?

Blue

Plan an investigation to find reactivity of three metals by their reaction with HCL acid

• Add metals to dilute HCl acid
• Measure the temperature change
• Same conc + vol of HCl acid
• Same mass/ moles of metals
• Same particle size of metal

Copper + HCl acid reaction

no reaction; no bubble or temp change

Limitations of a dot and cross diagram

doesn't show shape; only 2D

Why must water be kept away from sodium

the reaction is very exothermic and explosive; produces a corrosive solution; produces hydrogen which is explosive

Why are some reactions done in argon

argon is inert/ unreactive; so the reactants/ products don't react with oxygen or water vapour from the air