Atomic structure and the periodic table Flashcards
What is in a nucleus
- Neutrons
- Protons
What is the radius of a atom
0.1 nm
Radius of a nucleus
1 x 10*-14 m
What is the relative mass of protons, neutrons and electrons
proton - 1
neutron - 1
electron - very small
What is the relative charge of the neutron, electron and proton
Proton = +1 neutron = 0 electron = -1
What is the mass number on an atom in the periodic table
The top number
= total number of protons and neutrons in an atom
What is the atomic number
the bottom number and is the number of protons
elements
substances made up of atoms with the same atomic number
isotopes
atoms with the same number of protons but different number of neutrons
relative atomic mass
the average mass number of an element
Compounds
substances formed from two or more elements chemically bonded together in fixed proportions
Molecule
Particles containing two or more non-metal atoms bonded covalently
Mixtures
Substances are made up of different elements or compounds that aren’t chemically bonded to each other
example - air is a mixture (oxygen, carbon dioxide)
How can mixtures be separated
By physical methods like filtration
What is filtration
separates insoluble solids from liquids and solutions, it can be used to purify a liquid
Evaporation
Separates soluble salts from a solution
Crystallisation
Separates soluble salts from a solution
Simple distillation
separates solutions by heating up the solution and the liquid with the lower boiling point evaporates
Then cools and condenses and pours into a separate flask
As a result, two separated liquids
What is a disadvantage of simple distillation
Cannot separate liquids with similar boiling points
Fractional distillation
Watch video or look at book
History of the atom
. Plum pudding model (ball of positive with negative floating around)
- J J Thomspon
.Nuclear model - positive nucleus and a ball of electrons around, mostly empty space
- Ernest Rutherford
. Bohr model - electrons orbit nucleus in fixed shells
- Neils Bohr
.James Chadwick proved neutrons were neutral in the nucleus
Electronic structure
Electrons orbit around the nucleus in energy levels
The periodic table history
Before atomic structure was discovered, atomic weight was used to order elements
Mendeleev’s table
The elements were grouped by properties instead of strictly following atomic weight
swapped elements around in places where ordering didn’t fit the parrern
The modern periodic table
ordered by increasing atomic number
Group Number = The number of electrons in the outer shell
Period Number = The number of energy levels with electrons in
Metals
Elements that can form positive ions when they react
lose electrons
Non-metals
atoms that don’t generally form positive ions
gain electrons
How do metals and non-metals get a full outer energy level?
How are they more reactive?
metals - lose electrons
- They are more reactive when they lose electrons more easily
non-metals - gaining or sharing electrons
- They are more reactive when they gain or share electrons easier
When are metals and non-metals more reactive
metals - towards the bottom left of the periodic table
non-metals = towards the top right of the periodic table
What are 5 properties of metals
- shiny
- Strong but malleable
- high melting and boiling points
- good electrical conductor
- good thermal conductor
What are 4 properties of non-metals
- dull
- brittle (weak)
- low melting and boiling points
- Poor thermal and electrical conductor
What are the group one metals called
Alkali metals
What 3 things happen the further you go down group 1
reactivity - increases
melting and boiling points - decrease
relative atomic mass - increases
What are 3 properties of group 1 metals
_ They’re much more reactive
- They are less dense and softer
- Have lower melting points
Group 1 metals react with a range of substances to form ionic compounds
(3 of them)
metal + water –> metal hydroxide + hydrogen
metal + chlorine –> metal chloride
metal + oxygen –> metal oxide
Group 0 elements structure
noble gases
Non-metals with full outer shell
Their structure is stable so they are unreactive
As you go down group 0 boiling point increases
group 7 elements (halogens) appearance
fluorine - yellow gas
chlorine - dense green gas
bromine - volatile red/brown liquid
iodine - dark grey solid or purple vapour
as you go down group 7…
reactivity decreases, melting and boiling points increases, relative mass increases
metals electron transfer
lose electrons to form positive ions
non-metals
gain electrons to form negative ions
what is an ion?
charged particles made when electrons are transferred
ionic bonding?
occurs between positive metal ions and negative non-metal ions
properties of ionic compounds
giant ionic lattice, high melting and boiling points, conduct electricity when molten or dissolved
what is a covalent bond?
shared pair of electrons between two non-metal atoms.
what do molecular formulas show?
how many atoms of each element are in a compound
limitations of dot and cross diagrams
don’t show relative sizes of atoms or their arrangement in space
limitations of ball and stick diagrams
dont show which atoms the electrons in the bonds come from
limitations of displayed formula (h-n-h)
doesnt show 3D structure
simple molecular substances structure
covalent bonds between atoms are strong, intermolecular forces are weak
examples of simple molecular elements
hydrogen, oxygen, nitrogen, chlorine
examples of simple molecular compounds
hydrogen chloride, water, ammonia, methane
properties of simple molecular substances
low melting and boiling points - mostly gases or liquids at room temp.
dont conduct elec - no charged particles to carry charge.
what are giant covalent structures?
solids containing atoms which are all bonded to each other by strong covalent bonds
properties of giant covalent structures
high melting and boiling points - need lots of energy to overcome strong covalent bonds
dont conduct elec - no charged particles to carry charge
examples of giant covalent structures
diamond, graphite, silicon dioxide
what are polymers
very long chains of repeating units
polymer properties
usually solid at room temp because they have relatively strong intermolecular forces
diamond properties;
- bonding = carbon atoms form four covalent bonds
- high melting point
- doesnt conduct electricity
- very hard
graphite properties;
- bonding = carbon atoms form three covalent bonds. no covalent bonds between layers.
- high melting point
- conducts electricity ( has one delocalised electron )
- soft, slippery
graphene properties;
- bonding = carbon atoms form three covalent bonds
- high mp
- conducts electricity ( one delocalised electron )
- strong, light
first fullerene to be discovered?
buckminsterfullerene.
what is a fullerene?
any of a series of hollow carbon molecules that form either a closed cage (“buckyballs”) or a cylinder (carbon “nanotubes”).
what is a nanotube?
cylindrical fullerenes used in nanotechnology, electronics and materials. they have high length to diameter ratios.
four properties of metals;
high mp and bp, good thermal conductors, good electrical conductors, soft and malleable.
what is an alloy?
a mixture of a metal and at least one other element. harder than pure metals.
