key concepts Flashcards
what are the 4 state symbols
s - solid
l - liquid
g - gas
aq- aqueous
what is the formula of water
H2O
what is the formula of ammonia
NH3
what is the formula of carbon dioxide
CO2
what is the formula of hydrogen
H2
what is the formula of chlorine
CL2
what is the formula of oxygen
O2
what is the formula of ammonium
NH4+
what is the formula of hydroxide
OH-
what is the formula of nitrate
NO3-
what is the formula of carbonate
CO3 2-
what is the formula of sulphate
SO4 2-
common hazard symbols
oxidising
environmental hazard
toxic
harmful
highly flammable
corrosive
how did John Dalton describe atoms
as solid spheres
what did J J Thomson conclude
atoms were not spheres - idea of solid sphere had to change (plum pudding)
what did Rutherford conduct? and how?
gold foil experiment - fired positively charged alpha particles at an extremely thin sheet of gold
how did he disprove the plum pudding model could not be right?
they were expecting particles to pass straight through or be slightly deflected at most, but most of the particles did go straight through, however, some defective more than expected, and a small number were deflected backwards
what did Rutherford then come up with
the nuclear atom - atom we know today.
explain the bohr model
- electrons around nucleus of atom
- electrons in fixed orbit : nowhere between
- each cell has a fixed energy
how are scientific models backed up
peer review
mass & charge on a proton
mass: 1
charge: +1
mass and charge on a neutron
mass: 1
charge: 0
mass and charge on a electron
mass: 0.0005
charge: -1
facts about the nucleus of a atom
- middle of atom
- contains protons and neutrons
- positive charge
- nucleus is tiny compared to size of atom
facts about the electrons of the atom
- move around the nucleus in electron shells
- negatively charged
- tiny & shells cover a lot of space
- tiny mass
facts about atoms
- neutral (same number of protons and electrons)
however in ions:
- doesn’t have a equal amount of electrons meaning it has a overall charge (negative or positive)
which number on a symbol is the atomic
bottom
which number on a symbol is the mass number
top
23
Na which is the atomic number which is
11 mass number
atomic: 11
mass: 23
what does the atomic number tell you
number of protons
what does the mass number tell you
total number of protons and neutrons
how to find out how many neutrons are in the element
atomic - mass number
what are isotopes
different forms of the same element - same number of protons different number of neutrons which means they have the same atomic number but different mass number
what is the relative atomic mass
Average mass of one atom of the element compared to 1/12 of the mass of one atom
how to work out isotopic abundance
multiple each relative atomic mass by its isotope abundance and add up the results.
then divide the sum by the abundances
who made the first periodic table
Dmitri Medeleev
facts about Mendeleev’s table
- arranged around 50 elements
- sorted by properties
- put elements with similar chemical properties in columns
- he left gaps for undiscovered elements which he didn’t know yet for future people to fill in
facts about todays periodic table
- order of ascending atomic number
- similar chemical properties for columns called groups
- groups = number of electrons
- rows are called periods
- period = number of shells of electrons
what is a atoms electronic configuration
2,8,8
how to work out the electronic configuration
by atomic number
or
number of electrons in outer shell
what is a ion
a charged particle - can be single atoms or group of atoms
what is a negative ion called
anions
what does a negative ion do
gains electrons - more electrons than protons
what is a positive ion called
cations
what does a positive ion do
lose electrons - more protons than electrons
what groups most likely form ions
1 & 2
6 & 7
what do groups 1&2 do (ions)
lose electrons to form positive ions as they are metals
what do groups 6&7 do (ions)
gain electrons to form negative ions as they are non-metals
how do you work out the formula of a ionic compound
write the formulas for the elements
the overall charge must be 0 so work put the ratio that gives a overall neutral charge
what happens during ionic bonding?
when a metal or a nonmetal react together, the metal atom loses electrons to form a positive ion (cation) and the nonmetals gain these electrons to form a negative ion (anion). These oppositely charged ions are strongly attracted to one another, by electrostatic forces, this attraction is called an ionic bond.
how can ionic compounds formed be show
dot - cross diagram
what is a dot cross diagram
shows the arrangement of electrons in a atom or ion.
each electron is represented by a dot or a cross.
so these diagrams can show which atom the electrons in an ion originally came from.
what structure do ionic compounds have
regular lattice structure
what holds ionic compounds together
strong electrostatic forces of attraction between oppositely shafted ions, in all directions
what are the properties of ionic compounds
- high melting point and boiling point due to strong attraction, takes a lot of energy to break it
- don’t conduct electricity
- dissolve easy in water
3 types of models for ionic compounds
2D
dot cross diagram
3D models
all have advantages and disadvantages
what is a covalent bond
A strong bond that forms when a pair of electrons is shared between two atoms
how small are simple molecules
tiny
properties of simple molecular substances
- very strong covalent bonds
- melting and boiling points are low
- gas or liquid at room temp
- don’t conduct electricity
what is a polymer
molecules made up of long chains of covalently bonded carbon ions
properties of giant covalent structures
- bonded by strong covalent bonds
- high melting and boiling point
- don’t conduct electricity
- aren’t soluble in water
3 examples of giant covalent structures
diamond
graphite
graphene
features of diamond (giant covalent)
-made up of a network of carbon atoms that each form four covalent bonds
-strong covalent bonds, so diamond have a high melting point
-rigid lattice structure
-doesn’t conduct electricity
features of graphite (giant covalent)
-only forms three covalent bonds
-no covalent bonds: held together weakly (free to move around)
-high melting point
-conducts electricity
features of graphene (giant covalent)
-one atom thick
-sheet of carbon atoms joined together in hexagons
facts about metallic bonding
-giant structure
-electrons in outer shell are delocalised
-metallic bonding is very strong
-metallic bonding includes metallic elements and alloys
metallic bonding properties
-very high melting and boiling points
-aren’t soluble in water
-shiny solids at room temp
-atoms slide over eachother, therefore they are malleable
-good conductors of electricity and heat
difference between metals and non metals
-metals have metallic bonding non-metals dont
-different chemical properties
-non metals are more dull looking, metals are more shiny
what is mass
always conserved
what happens during a chemical reaction
no atoms destroyed
no atoms created
how to work out relative formula mass
use the periodic table to find relative atomic mass
add up relative atomic masses of all the atoms
if there’s a small number it means there 2 of everything inside the brackets
how to work out the empirical formula
start by finding the Mr of the empirical formula
divide by the Mr of the compound by the Mr of the empirical formula
to get the formula, multiple everything by the empirical formula
what is a mole
one mole of atoms or molecules of any substance will have a mass in grams equal to the relative particle mass for that substance
how to work out the number of moles
mass in grams/ Mr of compound
how to workout mass
moles x Mr
how to work out concentration
mass of solute / volume of solution
how to work out mass
concentration x Mr
how to calculate empirical formula from mass
-work out how many moles of each element you have
-work out the smallest whole number ratio to get empirical formula
how to calculate mass of a product from limiting reactant
-balance the equ
-work out relative formula mass
-find how many moles there are
-use balanced equ to work out how many moles there will be of the other substance
-use the number of moles to calculate mass
how can you balance equations using reacting masses
- divided the mass of each substance by its relative formula mass to find the number of moles
- divide the number of moles by the same amount to make them all numbers
- multiple all numbers by the same amount to make them all whole numbers
- write the balanced equ for the reaction
work out limiting reactants
- divide the mass of each substance to find the moles
- divide by the smallest number of moles
- compare the ratios between the moles of products with the balanced equ
