Atomic structure and the periodic table: full topic flashcards

What did scientists believe atoms were in the 1800’s?

Solid spheres that made up the different elements

Who created the plum pudding model?

JJ Thompson

Why did JJ Thompson disagree with the original definition of an atom in the 1800’s?

His measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles-electrons

What is the plum pudding theory?

Shows the atom as a ball of positive charge with electrons spread throughout the inside

Who were the scientists on the alpha particle scattering experiment?

Rutherford and his student

Explain how they conducted the alpha particle scattering experiment.

They fired positively charged alpha particles at an extremely thin sheet of gold

What did Rutherford expect from the alpha particle experiment vs what actually happened?

He was expecting the particles to pass straight through the sheet or to be slightly deflected

Whilst most particles did go through the gold sheet some were deflected more than expected and smaller numbers were deflected backwards

This proved the plum pudding model couldn’t be right

What was Rutherfords nuclear model?

• Tiny positively charged nucleus where the mass is concentrated

• A cloud of electrons surrounds the nucleus

• Most of the atoms are empty space

Explain what happened during the alpha particle scattering experiment with Rutherfords nuclear model.

• When alpha particles came near the concentrated, positive charge of the nucleus, they were deflected

• If they were fired directly at the nucleus, they were deflected backwards

• Otherwise they passed through empty space

Why did scientists believe Rutherfords nuclear model was wrong?

Scientists realised that electrons in a cloud around the nucleus of the atom, would attract to the nucleus causing it to collapse.

What was Bohr’s nuclear model?

• Suggested electrons were contained in shells

• Electrons orbit the nucleus in fixed shells

• Each shell is a fixed distance away fro the nucleus

This was supported by many experiments and helped explain lots of other scientists experiments at the time

How was the proton discovered?

Rutherford and other scientists showed the nucleus can be divided into smaller particles which have the same charge as the hydrogen nucleus

Who discovered neutrons?

James Chadwick carried out an experiment that provided evidence for neutral particles in the nucleus, now called neutrons

The discovery of which particle made a model of the atom that is most similar to the modern day accepted version?

The discovery of neutrons made it the most similar to the modern nuclear model.

What were the 2 obvious ways to categorise elements in the early 1800’s?

1. Their physical and chemical properties

2. Their atomic weight

Why were elements organised by their atomic weight in the early 1800’s?

• Scientists had not discovered protons or the atomic numbers

• They could only measure atomic weight

• When this was done the periodic pattern was noticed between the properties of the elements ( where the name ‘periodic table’ came from )

• The table was incomplete and some elements were placed incorrectly because it didn’t take into account their physical or chemical properties

How did Dimitri Mendeleev overcome the problems of old periodic table?

• rearranged 50 elements

• Mainly in order of atomic weight

• Switched the order if their properties meant it should be switched

Why were their gaps in Mendeleev’s periodic table and what did they lead to?

• Gaps were left to ensure the elements with similar properties stayed int he same groups

• Some of these properties indicated undiscovered elements

• This allowed Dimitri to predict what their properties might be

What later discovery confirmed Dimitri was right to not place elements in a strict order?

The discovery of isotopes-ensured different masses of the same elements were not placed in the wrong order because of their weight when their properties didn’t change

How are all the elements in the periodic table laid out?

In order of increasing atomic numbers

What does elements being in order of their atomic numbers cause in the modern periodic table?

Repeating patterns in their properties

What does the group number of an element tell you?

How many electrons it has in its outer shell

What trend is there for elements in the same group?

They are likely to react similarly

Give 2 examples of properties you can predict from elements being in the same group.

1. how or what with they might react

2. if their reactivity increases or decreases as you go down the group

What elements are in group 1?

Lithium, sodium, potassium, rubidium, caesium and francium

How many electrons are in there outer shells and how does it effect their reactivity for group 1 elements?

• They have 1 electron in their outer shell

• Makes them very reactive

• Lose electrons easily to form ions and react with other elements

What are the 3 main properties of all group 1 metals?

1. soft metals

2. low density

3. very reactive

What are the trends as you go down group 1 metals?

1. Increasing reactivity

2. Lower melting and boiling points

3. Higher relative atomic masses

Why does the reactivity increase as you go down group 1?

The outer electron is more easily lost as the attraction between the nucleus and the electron decrease because the electron is further away from the nucleus the further down the group you go

What bond do group 1 metals form with what elements?

Ionic compounds with non-metals

What are the properties of group 1 compounds?

white solids that dissolve in water to form colourless solutions

How do group 1 elements react with water?

• React vigorously to produce hydrogen gas and metal hydroxides

• These compounds dissolve in water to produce alkaline solutions

• The more reactive the metal, the more violent the reaction

• The amount of energy given out the the reaction increases down the group

2 Na ( s ) + 2 H 2 O ( l ) → 2 NaOH ( aq ) + H 2 ( g )

How do group 1 elements react with chlorine?

• React vigorously when heated in chlorine gas

• Forms white metal chloride salts

• Reactivity increases as you go down the group, so the reaction with chlorine gets more vigorous

2 Na ( s ) Sodium + Cl 2 ( g ) Chlorine → 2 NaCl ( s ) Sodium Chloride

How do group 1 elements react with oxygen?

• Form metal oxides

• Different types of oxides form depending on the metal:

  1. Lithium-lithium oxide (Li₂O)

  2. Sodium- sodium oxide (Na₂O), sodium peroxide (Na₂O₂)

  3. Potassium - potassium peroxide(K₂O₂), Potassium superoxide (KO₂)

4 N a + O 2 → 2 N a 2 O

How do alkali metals compare to transition metals?

1. Group 1 metals are much more reactive

2. React more vigorously with oxygen water and the group 7 elements

3. Less dense, strong and hard

4. Group 1 metals have much lower opt and bpt

What are the subatomic particles in an atom?

Neutrons protons and electrons

Explain where and what the nucleus is.

• In the middle of the atom

• Contains neutrons and protons

• the radius is about 1 ×10^-14

• It has a positive charge because of the protons

• Almost the whole mass of the atom is concentrated at the nucleus

Explain where and what electrons are in an atom?

• Move around the nucleus in shells

• Negatively charged

• The volume of their orbits determine the size of the atom

• Electrons has virtually no mass

What are the masses and charges of subatomic particles?

Do atoms have a charge?

No they are neutral because they have the same number of protons and electrons

Why do ions have charges?

The proton and electron numbers aren’t equal so the charges do not cancel out

What does the atomic number tell you?

How many protons there are

What does the mass number tell you?

the total number of protons and neutrons in an atom

Where are the atomic number and atomic mass on a nuclear symbol?

What is the definition of an element?

a substance made up of atoms that all have the same number of protons

What is the role of protons in an element?

Decides what type of atom it is

What is the definition of an isotope?

different forms of the same element, which have the same number of protons but different numbers of neutrons

What is relative atomic mass?

average mass taking into account the different masses and abundances of all the isotopes that make up that element.

What is the formula for relative atomic mass?

A_r = sum of (isotope abundance x isotope mass number) / sum of abundances of all the isotopes

How is a compound formed?

atoms react to form compounds

What is the definition for a compound?

substances formed from 2 or more elements, that are chemically bonded in fixed proportions

How are chemical bonds made in compounds ?

taking in, removing or sharing electrons

Why are compounds difficult to separate?

A lot of energy is needed to separate the chemical bonds

What is ionic bonding?

• compound formed from a metal and non-metal

• Metal loses electrons to form positive ions

• non-metal gains electrons to form negative ions

• The opposite charges mean they are strongly attracted to each other

What is covalent bonding?

• A compound formed from non-metals

• Each atom shares an electron with another atom

What are the chemical formulas for:

• carbon dioxide

• ammonia

• water

• sodium chloride

• carbon monoxide

• hydrochloric acid

• calcium chloride

• sodium carbonate

• sulfuric acid

What is the definition of a mixture?

a substance made of 2 more more elements or compounds that are not chemically bonded

Explain the method of the chromatography practical.

1. Draw a line near the bottom of the filter paper sheet ( with pencil because its insoluble)

2. Add a drop of ink onto the line and place it into a beaker of solvent

3. The solvent depends on what is being tested-some compounds dissolve well in water however others may require stronger solvents such as ethanol

4. Make sure the ink isn’t touching the solvent

5. Place a lid on top of the container to prevent the solvent evaporating

6. The solvent seeps up the paper carrying the ink with it

7. Each dye in the ink will move up the paper at different rates so the dyes will separate

8. Any insoluble dyes will stay on the baseline

9. When the solvent has nearly reached the top of the paper take it out and let it dry.

10. This will result in the creation of a chromatogram

What is chromatography used for?

Separating substances in a mixture based on their solubility

Explain why you use pencil to draw the baseline in chromatography.

Pencil is insoluble and therefore will not dissolve and seperate with the solvent

Explain why the dyes seperate with the solvent in chromatography .

Each dye will move up the paper with the solvent at different rates causing them to separate

What will happen to dyes that are insoluble in chromatography?

They will stay on the baseline

What is the pattern called that forms at the end of a chromatography test?

chromatogram

When can filtration be used s a separation method?

When your product is an insoluble solid that needs to be separated from a liquid reaction mixture

Can be used to filter solid impurities in a reaction mixture

When can you use evaporation as a separation technique?

to separate a soluble solid from a solution, if the salt won’t decompose when heated

Explain the process of evaporation as a separation technique

1. Pour solution into an evaporating dish

2. Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. eventually crystals will start to form

3. Keep heating the evaporating dish until you are left with dry crystals

When should you use crystallisation as a separation technique?

To separate a soluble solid from a solution when the desired salt will decompose when heated or when you want big crystals of a salt

Explain the process of crystallisation as a separation technique

1. Pour solution into an evaporating dish and gently heat the solution. Some of the solution will evaporate and the solution will get more concentrated.

2. Once some of the solvent has evaporated or you see crystals starting to form, remove the dish from the heat and leave solution to cool

3. The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution

4. Filter the crystals out of the solution and leave them in a warm place to dry. You could use an oven or desiccator

What is rock salt?

a mixture of salt and sand

How and why can you separate rock salt to only get the salt?

Salt is soluble will sand is in soluble

1. Grind the mixture to make sure the salt crystals are small so they will dissolve easily

2. Put the mixture in water and stir so the salt dissolves and the sand doesnt

3. Filter the mixture. The sand will be your residue and the solvent will be your salt solution

4. Evaporate the water from the solution so the salt forms dry crystals

What is distillation used for?

Separate a mixture of liquids according to their boiling points

What is simple distillation?

Used to separate a liquid from a solution

Explain the process of simple distillation.

1. The solution is heated. The part of the solution with the lowest boiling point evaporates first

2. The vapour is then cooled, condenses and is collected

3. The rest of the solution is left in the flask

How can you use simple distillation to get pure water from seawater?

The water evaporates and is condensed and collected. eventually you will end up with just salt in the flask

What is a problem with simple distillation?

You can only separate liquids with a significant difference in boiling points otherwise the temperature will increase so both liquids evaporate and become a mixture again when collected

What is fractional distillation used for?

To separate a mixture of liquids with similar boiling points

Where is fractional distillation used on a much larger scale?

Used for the separation of crude oil

Explain the process of a lab fractional distillation

1. Put your mixture in a flask and stick a fractioning column on top and then heat it.

2. The different liquids have different boiling points so will evaporate at different temperatures

3. The liquid with the lowest boiling point evaporates first. Then the thermometer matches the boiling point of the liquid it will reach the top of the column

4. Liquids with higher boiling points may start to evaporate, but the column is cooler towards the top so they will only reach part way up before condensing and running down towards the flask

5. When the first liquid has been collected you raise the temperature until the next liquid reaches the top.

6. Repeat this until you have collected all the liquids separately

How do atoms generally gain a full outer shell?

By losing or gaining electrons

Why do metals form positive ions easily?

• Don’t have many electrons to lose

• Electrons towards the bottom’s electrons are far away from nucleus so have weaker intermolecular forces

Why do non-metals form positive ions, and how do they gain a full outer shell?

They are often only missing a small number of electrons

Easier to share or gain electrons

What causes metals to have similar properties?

metallic bonding

What are the properties of metals?

• Strong and malleable

• Conduct heat and electricity

• High melting and boiling points

• Shiny

• Have high densities

What are the properties of non-metals?

• Dull

• Brittle

• Aren’t always solids

• Insulators

• have a lower density

What are the properties of transition metals?

• Conduct heat and electricity

• dense

• strong

• shiny

• Can form more than one type of ion

• Ions are often coloured so form colourful compounds

• Make good catalysts

What are the group 7 elements called?

Halogens

Explain what the following elements are in terms of colours and properties:

Flourine

Chlorine

Bromine

Iodine

Fluorine: very reactive, poisonous, yellow gas

Chlorine: fairly reactive, poisonous, dense green gas

Bromine: Dense, poisonous, red-brown volatile liquid

Iodine: Dark grey crystalline solid or purple vapour

What are the trends as you go down group 7?

• less reactive: harder to gain an extra electron because the outer shell is further from nucleus

• High mot and bpt

• higher relative atomic masses

What compounds and with what bonds do halogens form when they react with non-metals?

molecular compounds via covalent bonding

What bonds do halogens form with metals?

Ionic bonds

What ions do halogens form when bonded with metals?

1- ions called halides when bonded with metals

How do displacement reactions between halogens work?

• occurs between a more reactive halogen and the salt of a less reactive one

What are the group 0 elements called?

Noble gases

What are the properties of noble gases?

• full outer shells

• Inert (don’t react much or at all)

• monatomic gases (don’t react with each other)

• Colourless at room temperature

• Non-flammable

What are the properties of noble gases as you go down the group?

• Bpt increases

• mass increases

Why does the boiling point of noble gases increase as you move down the group?

Increase in the number of of electrons in each atom leading to greater intermolecular forces between them which we need t overcome.