Atomic Structure and the Periodic Table Flashcards
What is in the nucleus?
Protons and Neutrons
Electrons _____ the nucleus in ______ ____
Orbit
Electron shells
Atoms have the same number of _______ and _______
Protons
Electrons
Why do atoms have no charge?
The positive charge of the protons cancel out the negative charge of the electrons
Neutrons have no charge
Mass of neutron:
1
Mass of proton:
1
Mass of electron:
Very small 0.000000005
Charge of proton:
+1
Charge of neutron:
0
Charge of electron:
-1
What is the mass number of an element?
The total number of protons and neutrons in the nucleus of the atom
What is the atomic number of an element?
The number of protons in the nucleus of the element
What are isotopes?
Different forms of an element, that have the same number of protons but a different number of neutrons
What is a compound?
A substance made from 2 or more elements that are chemically bonded
What is needed to separate compounds into its original elements?
A chemical reaction
What is a mixture?
Elements that are mixed together - no chemical reaction
Can a mixture be seperated out?
Yes by physical methods
Properties of ________ are usually different from the properties of the ________ element
Compounds
Original
Properties of ________ are a mix of the properties of the ________
Mixtures
Elements
What is chromatography used to separate?
Mixtures (of coloured compounds such as dyes)
What is the solvent?
The liquid
Why use a pencil to mark during chromotography?
Its insoluble
Why should the compounds NOT touch the solvent?
The compounds will dissolve in it
What will the movement of a dye be if its insoluble?
It will stay on the baseline
What is filtration used to separate?
Insoluble solids from liquids
What is evaporation used to separate?
Solids from solutions
What dish is used during evaporation?
An evaporating dish
What is crystallisation used to separate?
Soluble solids from solutions if the salt decomposes when heated
When does evaporation not work?
If the salt decomposes when heated
During crystallisation what do you do after evaporating the solution to form salt crystals?
Filter the crystals out of the solution
How do you separate rock salt?
Dissolve the salt in water
Filter the mixture - removes rock
Evaporate the water - leaves salt as crystal
What is distillation used to separate?
Mixtures which contain liquids
What is simple distilliation used to separate?
A liquid from a solution
What is fractional distillation used to separate?
A mixture of liquids (more than 1)
Simple distillation can only be used to separate things with …….
Very different boiling points
What happens during simple distillation?
The solution is heated - liquid with lowest boiling point evaporates
Vapour is cooled by a condenser and collected
What happens during fractional distillation?
Heat the mixture
Different liquids evaporate at different temps
When one liquid evaporates at its boiling point, it will reach the top of the column
Other liquids that start evaporating will only get a certain way before condensing
John _______ said that all matter was made up of ______ which are _____ ______
Dalton
Atoms
Solid spheres
What did JJ Thompson conclude?
The plum pudding model
Who thought of the plum pudding model?
JJ Thompson
What is the plum pudding model?
That an atoms a ball of positive charge with negatively charged electrons stuck inside it
Who conducted the alpha particle scattering experiment?
Ernst Rutherford
What did Ernst Rutherford do?
He fired positively charged alpha particles at a thin sheet of gold
What was assumed would happen in the alpha particle scattering experiment?
That particles would pass through the sheet or be slightly deflected at most
What actually happened in the alpha particle scattering experiment?
Some particles were deflected more than expected and a small number were deflected backwards while most did go straight through
How is the nuclear model used to explain the alpha particle scattering experiment?
The atom has a tiny positively charged nucleus at the centre, where most of the mass is concentrated
A ‘cloud’ of negatively charged electrons surround the nucleus with most of the atom being empty space
Why were some particles deflected backwards in the alpha particle scattering experiment?
Because, when the alpha particles came near the concentrated positive charge of the nucleus, they repelled (alpha particle is positively charged)
What did Neils Bohr realise?
That if there is a ‘cloud’ of electrons, the electrons would be attracted to the nucleus, causing the atom to collapse
What did Neils Bohr suggest?
That electrons orbit the nucleus in fixed shells
Who suggested that electrons orbit the nucleus in fixed shells?
Niels Bohr
Who discovered the nucleus?
James Chadwick
How many electrons can go in each shell?
2
8
8
Atoms want to have a ___ outer shell of electrons
Full
Who had the atomic theory (periodic table)?
John Dalton
Who decided to group elements into Traids?
Johann Dobereiner
How did Johann Dobereiner group elements?
He grouped them into triads, based on similar appearance and reactions
Who decided to group elements into the Law of Octaves?
John Newlands
How did John Newlands group elements?
He grouped them into the Law of Octaves, in the order of their relative atomic mass
Who arranged the Table of Elements?
Dimitri Mendeleev
How did Mendeleev order elements?
In order of increasing atomic weight but switched and placed some out of order to appear in the same column as other elements with similar properties
Why did Mendeleev reorder some elements?
So that elements would be in the same column as other elements with similar properties
Why did Mendeleev leave spaces?
For atoms that are yet to be discovered - gaps allowed Mendeleev to predict the properties of these undiscovered elements
What discovery confirmed that Mendeleev was correct to not place elements in a strict order of atomic mass?
Isotopes
What did the discovery of isotopes confirm?
That Mendeleev was correct to not place elements in a strict order of atomic mass
What are atoms in order of in the modern periodic table?
Increasing atomic (proton) mass
What does the group number tell?
How many elements there are in the outer shell
What does the way atoms react depend on?
How many electrons there are in the outer shell, groups reacts similarly
Properties of metals:
Strong
Malleable
Good conductors of heat and electricity
High melting and boiling points
Properties of non-metals:
Dull Brittle Not always solid at room temp Don't generally conduct Generally have a lower density
What are unique about transition metals?
They can have more than one ion
They are often coloured so compounds that contain them are colourful
They often make good catalysts
What are Group 1 metals called?
Alkali metals
Properties of alkali metals:
Soft
Low density
As you go down Group 1:
Higher relative atomic mass
Lower melting and boiling points
Increasing reactivity
Why does the reactivity of alkali metals increase as you go down the group?
The outer electron is lost more easily as the attraction between the outer shell electron and the nucleus decreases because the electron is further away from the nucleus as you go down the group, meaning there is more electron shielding, so not as much energy is needed to lose the other electron to form a full outer shell
What do alkali metals react with?
Non-metals
What do alkali metals form when they react with non-metals?
Ionic compounds
What colour solution is generally formed when alkali metals when dissolves in water?
Colourless
Alkali metals react ________ with water
Vigorously
What is produced when alkali metals react with water?
Hydrogen gas and metal hydroxides
What solutions do metal hydroxides produce when dissolved in water?
Alkaline
Alkali metals react ________ with chlorine
Vigorously
What is formed when alkali metals are heated in chlorine gas?
White metal chloride salts
What is formed when alkali metals react with oxygen?
A metal oxide
Alkali metals burn with a ________ flame when reacted with oxygen
Coloured
Compared to transition metals, alkali metals…
Are less dense, strong and hard
Have lower melting points
How many electrons are there in the outer shell of halogens?
7
`As you go down Group 7:
Higher melting and boiling points
Higher relative atomic mass
Less reactive - harder to gain an extra electron - outer shell is further away
Why does the reactivity decrease as you go down Group 7?
Because the outer electron shell is further away from the nucleus, meaning there is more electron shielding, meaning it is harder to attract an electron to the nucleus
How do halogens share electrons?
Via covalent bonding
How do halogens achieve a full outer shell?
They share electrons with other non-metals via covalent bonding
What kind of compounds are formed when halogens react with non metals?
Compounds with simple molecular structures
What charge ions do halogens form when they bond with metals?
1- ions
What kind if compound is formed when metals and halogens bond?
Ionic compounds
What are group 0 elements also called?
Noble gases
Properties of noble gases:
Inert - unreactive
Colourless
Why are noble gases inert?
They have a full outer shell that is energetically stable so they don’t need to gain or lose electrons
Noble gases exist as _________ gases
Monatomic
What are monatomic gases?
Single atoms not bonded to each other
Why are noble gases colourless and non-flammable?
Because they are inert
What is the trend in the boiling point of noble gases?
It increases as you go down the group
Why does the boiling point of noble gases increase as you go down the group?
Because there is an increase in the number of electrons in each atom, meaning there are greater intermolecular forces that have to be overcome
