Science - Chemistry - Atomic Structure - C1 Flashcards
what is an atom ?
the smallest part of an element that can exist
what is an element ?
a substance made of one type of atom only
what are chemical symbols ?
symbols that represent elements
what element is O ?
oxygen
what is the chemical symbol for sodium ?
Na
how are groups on the periodic table arranged ?
numbered, from 1 to 7 then 0
what side of the stepped line are non - metals ?
right side
what is a chemical formula used for ?
representing and element or compound in balanced chemical equations
what is a compound ?
a substance formed by the chemical union of 2 or more elements
what is a balanced chemical equation ?
a chemical equation written using the symbols and formulae of reactants and products, so that the number of units of each element present is the same on both sides of the arrow
what is a molecule ?
a collection of 2 or more atoms held together by chemical bonds
how many hydrogen atoms and oxygen atoms are in h20 ?
hydrogen - 2 oxygen - 1
what are chemical reactions ?
a change in which atoms are rearranged and joined together differently to make new substances
what is an ion ?
an electrically charged particle, formed when an atom or molecule gains or loses electrons
what is an ionic compound ?
when a negative ion joins with a positive ion
what is a negative ion ?
an ion that has gained an electron
what is a positive ion ?
an ion that has lost an electron
what is a word equation ?
an equation in which only the names of the products and reactants are used to model a reaction
what is a reactant ?
a substance that reacts together with another substance to form products in a chemical reaction
what is a product ?
a substance formed in a chemical reaction
show products and reactants in a word equation
reactants -> products
potassium hydroxide reacts with sulfuric acid. potassium sulfate and water are formed in the reaction, show this in a word equation
potassium hydroxide + sulfuric acid -> potassium sulfate + water
what are state symbols ?
a symbol used in a chemical reaction to see if the substance is a solid, liquid, gas or aqueous solution
what are the state symbols for solids, liquids, gases and aqueous ?
s - solid l - liquid g - gases aq - aqueous
what is the law of conservation of mass ?
the total mass of reactants before a reaction is equal to the total number of products after a reaction, because no atoms can be created or destroyed so the mass must be unchanged
balance - N2 + H2 -> NH3
N2 + 3H2 -> 3NH3
what is a ‘pure’ substance ?
a substance that consists of only one element or compound
what is a mixture ?
a mixture consists of 2 or more different substances, not chemically combined
can different substances in a mixture be separated ?
yes, mixtures can be separated by a physical process, that do not involve chemical reactions and no new substances are made
what is filtration ?
method used to separate insoluble solid from a liquid using a physical barrier such as filter paper
how does filtration work ?
filter paper has tiny holes in it, which are large enough to let small molecules and dissolved ions through but not the larger particles of undissolved solid
explain filtration (experiment)
- 1 beaker contains mixture of solid and liquid, the other contains a funnel with filter paper
- solid and liquid mixture is poured into filter funnel
- liquid drips through the filter paper but solid particles are caught in the filter paper
what is crystallisation ?
process of producing crystals from a solution by evaporating the solvent
explain crystallisation (experiment)
- solution is placed in an evaporating basin and heated with a bunsen burner
- volume of solution has decreased as some water has evaporated, solid particles begin to form in the basin
- all water has evaporated, leaving solid crystal behind
give an example of a solution that uses crystallisation
copper sulfate - copper sulfate crystals form from copper sulfate solution
what is simple distillation ?
separation method used to separate a solvent from a solution
what is a solvent ?
the liquid in which the solute dissolves to form a solution
what is a solution ?
mixture formed by a solute and a solvent
what is a boiling point ?
temperature at which a substance changes quickly from liquid to gas
define dissolved
when a substance breaks up and mixes completely with a solvent to produce a solution
what is a vapour ?
gas formed below the boiling point of a substance
what is condensation ?
a change in state in which a gas becomes liquid by cooling
how does simple distillation work ?
the dissolved solute has a higher boiling point than a solvent
when solution is heated, solvent vapour leaves the solution and becomes cooled and condensed.
the remaining solution becomes more concentrated as the amount of solvent in it decreases
explain simple distillation (experiment- seawater/salty water)
- salty water is heated
- water vapour cools in the condenser and drips into a beaker
- the water is condensed and is now in a beaker the salt stays behind
what is fractional distillation ?
a mixture of several substances is distilled, and the evaporated components are collected as they condense at different temperatures
give an examples of when fractional distillation is used ?
useful for separating ethanol and water
how does fractional distillation work ?
different liquids have different boiling points
explain fractional distillation (experiment- water and ethanol)
-water and ethanol solution is heated
-ethanol evaporates first, cools, then condenses
- the water left evaporates, cools, then condenses
what is chromatography ?
chromatography is used to separate different substances dissolved in a liquid
explain paper chromatography (experiment)
-water and ethanol solution is heated
- as paper is lowered into the solvent, some of the dye spreads up the paper
-the paper absorbs the solvent, the dye has spread further up the paper
name the 2 stages in chromatography ?
-stationary phase
-mobile phase
what is the stationary phase in chromatography ?
the phase in chromatography that does not move, e.g the paper in chromatography
what is the mobile phase in chromatography ?
phase in chromatography that moves, e.g solvent or mixture of solvents
what is a chromatogram ?
the results of separating mixtures in chromatography
what does a pure substance produce on a chromatogram ?
1 spot
what does an impure substance produce on a chromatogram?
2 or more spots
a chromatograph can be used to identify substances by comparing them with known substances. when are 2 substances likely to be the same ?
- if they produce the same number of spots
- if they match in colour
- if the spots travel the same distance up the paper
how did scientists first organize elements in the periodic table?
by atomic weight/ relative atomic mass
what is relative atomic mass ?
the mean relatives of the mass of the different isotopes in an element
who published the first periodic table ?
Dmitri Mendeleev
why did Mendeleev leave gaps in his periodic table ?
for elements that weren’t known at the time
how are elements arranged in the modern periodic table ?
arranged in rows called periods, in order of increasing atomic number
elements with similar properties are placed in vertical columns called groups
why was there a pair reversal between iodine and tellurium ?
iodine has one naturally occurring isotope, iodine 127
the most abundant tellurium isotopes are tellurium-128 and tellurium-130
The high relative abundance of these tellurium isotopes gives tellurium the greater relative atomic mass. The atomic number of tellurium is 52 and the atomic number of iodine is 53, so these elements are in the correct order in the modern periodic table.
what is an isotope ?
atoms an element with the same number of protons and electrons but different number of neutrons
what is an electronic structure ?
the way in which electrons are arranged in an atom
what is the maximum number of electrons that can occupy the first shell ?
2
how is electronic structure linked to the elements position in the periodic table ?
number of shells - period number
number of electrons in outer shell - group number
numbers added together - atomic number
do metals gain or lose electrons in their chemical reactions ?
lose electrons
do metals form positive or negative ions ?
positive ions
do non metals form positive ions ?
no
compare physical properties of metals and non metals
metals : high melting and boiling point
good conductor of heat
good conductor of electricity
shiny
high density
malleable
ductile
non metals: low melting and boiling point
poor conductor of heat
poor conductor of electricity
dull
low density
brittle
how many electrons do group 1 metals have in their outer shell ?
1
what groups in the periodic table are non metals ?
groups 6, 7, and 0
do atoms of non metals gain or lose electrons ?
gain
do atoms of non metals form positive or negative ions ?
negative ions
what was John Daltons ideas about atoms in 1803?
he thought all matter was made out of atoms which were tiny spheres which could not be divided
what did JJ Thompson discover about atoms ?
electrons
what were JJ Thompsons ideas about atoms ?
the plum pudding model - atoms were a ball of positive charge with negative electrons embedded in it
what experiment did Ernest Rutherford carry out?
an experiment to test the plum pudding model, positively charged alpha particles were fired at thin gold foil, most particles fired straight through the foil but a few were scattered in different directions
what atomic model did Ernest Rutherford discover ?
the nuclear model -
-the mass of an atom is concentrated at its centre, the nucleus
-the nucleus is positively charged
how did Niels Bohr adapt Ernest Rutherford’s nuclear model ?
he discovered that electrons orbit the nucleus in shells, leading to the idea that the nucleus contained small particles with positive charge called protons
what did James Chadwick discover ?
protons, particles in the nucleus with mass but no charge
what subatomic particles does the nucleus contain ?
protons and neutrons
what are the masses of the 3 subatomic particles?
protons - 1
neutrons - 1
electrons - very small
which subatomic particle is the same as an elements atomic number ?
protons
do atoms have the same number of protons and electrons ?
yes
what is the mass number ?
the number of protons and neutrons in an atom
how do you calculate the number of subatomic particles in an atom ?
number of protons - atomic number
number of electrons - atomic number
number of neutrons - mass number - atomic number
do isotopes of an element have the same atomic number or the same mass number ?
atomic number
how do you calculate relative atomic mass ?
total mass of atoms
______________________
total number of atoms
do group 0 elements contain metals or non-metals ?
non-metals
what are group 0 elements known as and why ?
noble gases, they exist as single atoms-unreactive
do noble gases have high or low boiling points ?
low boiling points
why are group 0 elements unreactive ?
they all have a full outer shell of electrons, so they do not need to react as they do not need to lose, gain, or share electrons
what are the group 1 metals known as ?
the alkali metals
state properties of group 1 metals
- they are soft
- have relatively low melting points
- have low densities
going down the group 1 metals, does the melting point increase or decrease ?
decrease
in a chemical reaction, do group 1 metals lose or gain electrons ?
lose
when reacting with water, what do group 1 metals produce ?
a metal hydroxide + hydrogen
when reacting with water, do the reactions become more or less vigorous as you go down the group 1 elements ?
more vigorous
do group 1 elements burn calmly or vigorously in oxygen ?
vigorously
do group 1 elements react calmly or vigorously with chlorine ?
vigorously
as you go down group 1, what happens to the elements ?
- they get larger
- the outer electron becomes further from the nucleus
- the force of attraction between the nucleus and the outer electron decreases
- the outer electron is lost more easily
what are group 7 elements known as ?
halogens (non - metal)
the further you go down group 7, does the relative atomic mass become higher or lower ?
higher
how are halogens ‘simple’ molecules ?
each molecule is made up of a pair of halogen atoms joined by a single covalent bond
as you go further down group 7, does the melting and boiling point increase or decrease ?
increase
how many electrons are in the outer shell of group 7 elements ?
7
do group 7 elements form positive or negatively charged ions ?
negative
when reacting with metals, what do halogens produce ?
salts
as you go down group 7, does the reactivity increase or decrease ?
decrease
chlorine + potassium iodine —->
potassium chloride + iodine - gets displaced as chlorine is more reactive than iodine
going down group 7, what happens to the elements ?
- the atoms become larger
- the shell becomes further away from the nucleus
- force of attraction between nucleus and outer shell decreases
- an outer shell electron is gained less easily
- halogen becomes less reactive
- they get darker
what is a transition metal ?
a metal that is inbetween group 2 and 3 in the periodic table and has coloured compounds
what physical properties do transition metals share with all metals?
- conduct electricity in solid and liquid states
- are shiny when freshly cut
what physical properties to transition metals typically have, that other metals do not ?
-have higher melting points
- higher densities
- greater strength
- greater hardness
how do transition metals react with oxygen compared to group 1 elements ?
group 1 elements react quickly with oxygen, wheras transition metals react slowly or not at all
how do transition metals react with water compared to group 1 elements ?
group 1 elements react vigorously with water, wheras transition metals react slowly or not at all
how do transition metals react with halogens compared to group 1 elements ?
group 1 elements react vigorously with halogens, and some transition metals react with halogens
what is a catalyst ?
a substance that changes the rate of a chemical reaction without being changed by the reaction itself
