T1 atomic structure and the periodic table Flashcards
what is an atom
smallest part of an element what can exist
what is an element
substance of only one type of atom
what 2 groups can elements be classified into
metals and non-metals
what is a compound
two or more elements combined chemically in fixed proportions which can be represented by formulae
do compounds have the same properties as their constituent elements
no, they have different properties
what is a mixture?
does it have the same chemical properties as its constituent materials?
mixture consists of two or more elements or compounds not chemically combined together
does have the same chemical properties
what are the methods through which mixtures can be separated
do these involve chemical reactions
filtration, crystallisation, simple distillation, fractional distillation, chromatography
don’t involve chemical reactions
describe and explain simple distillation
used to separate liquid from a solution - the liquid boils off and condenses in the condenser
thermometer will read the boiling point of the pure liquid, get to keep the liquid
describe and explain crystallisation
solution is heated and some of the solvent evaporates, leaving behind a saturated solution
saturated solution is allowed to cool and crystals to form
crystals can be separated by filtration
describe and explain evaporation
technique for separation of a solid dissolved in a solvent from a solvent (eg salt from H2O)
solution is heated until all the solvent evaporates, the solids stays in the vessel
describe and explain fractional distillation
technique for separation of a mixture of liquids, works when liquids have different boiling points
the fractionating column contains glass beads, helps to separate the compounds
industry - mixtures are repeatedly condensed and vapourised
column is hottest at bottom and coldest at top
liquids will condense at different heights
describe and explain chromatography
place a piece of paper with a spot containing a mixture in a beaker with some solvent
bottom of paper has to be in contact with the solvent
solvent level will slowly start to rise, separating the spot into few spots
what is a separating funnel
apparatus for separating immiscible liquids
two immiscible liquids of different densities will form two distinct layers in the separatory funnel
can run off the bottom layer (liquid with greater density) to a separate vessel
describe the plum-pudding model
atom is a ball of positive charge with negative electron embedded in it
describe the Bohr/nuclear model and how it came about
suggests that electrons orbit the nucleus at specific distances (shells) - came about from the alpha scattering experiments
what did the work of James Chadwick provide evidence for
existence of neutrons in the nucleus
relative masses and relative charges of the proton, neutron and electron
Masses: 1, 1, very small
charges: 1, 0, -1
radius of an atom
0.1 nm
radius of a nucleus and what is it compared to that of the atom
1x10-14 m and 1/10000
name given to the number of protons in the nucleus
atomic number
atoms of the same element have the same number of which particle
protons
what is the mass number
total number of protons and neutrons
equation for the number of neutrons using mass number and atomic number
subtract atomic number from the mass number
what is an isotope
do isotopes of an element have the same chemical properties
atoms of the same element that have a different number of neutrons
have the same chemical properties as they have the same electron structure
what is the relative atomic mass
average mass value which takes the mass and abundance of isotopes of an element into account, on a scale where mass of 12C is 12
what are ions
charged particles
formed when atoms lose (positive ions) electrons or gain (negative ions) electrons
properties of metals
high boiling/melting point conducts heat and electricity shiny malleable high density basic oxides
properties of non-metals
low boiling/melting point don't conduct heat or electricity - minus graphite dull brittle low density acidic oxides
what is formed when a metal reacts with a non-metal
ionic compound (made of positive and negative ions)
what is formed when a non-metal reacts with a non-metal
molecular compound containing covalently bonded atoms
atoms share electrons, as opposed to transferring electrons between each other
group 0 elements are known as
noble gases
what makes the periodic table periodic
similar properties of elements occur at regular intervals
elements in the same group have the same number of electrons in their outer shell; what does this tell us about their chemical properties
they have similar chemical properties
early periodic tables were arranged by
increasing atomic mass
knowledge of what made it possible to explain why the order based on atomic weights was not always correct
isotopes
elements that react to form positive ions are
metals
elements in group 1 are known as
alkali metals
state three characteristics of the alkali metals
1 electron in outer shell
low density
are stored under oil to prevent reactions with oxygen or water
soft, can be cut with a knife
how do group 1 elements react with non-metals
why are these reactions similar for the different group 1 elements
form ionic compounds which are soluble white solids which form colourless solutions
all have 1 electron in outer shell
how do group 1 elements react with water
release hydrogen and form hydroxides which dissolve to form alkaline solutions
react vigorously with water fizzing and moving around on the surface of water
how does reactivity change moving down group 1
why
increases as the atoms get larger and the distance between the nucleus and the outer electrons increases thus, the attraction from the nucleus decreases, allowing them to easily lose electrons
state 5 characteristics of group 7
7 electrons in outer shell coloured vapours diatomic molecules form ionic salts with metals form molecular compounds with non-metals
state 5 group 7 elements and states of matter of molecules they form
F2 is a pale yellow gas
Cl2 is a pale green gas
Br2 is a dark brown liquid
I2 is a grey solid
state 3 changes that occur in group 7 as one moves down the group
higher relative molecular mass
higher melting and boiling point
less reactive - less easily gain electrons
a more reactive halogen displaces a less reactive one from an aqueous solution of iits salt; explain the trend in reactivity of halogens in these reactions
reactivity decreases down the group
as we go down the group, the atoms get larger, so an incoming electron will be less tightly held by the attractive forces from the nucleus
compare group 1 metals and transition metals
G1 and transition metals are heat and electricity conductors, shiny when polished and form ionic compounds with non-metals
transition metals have higher densities and higher melting points, less reactive and harder than group 1 metals
state 3 common characteristics of transition metals
ions with different charges
coloured compounds
catalytic properties
what is a catalyst
chemical substance that increases the rate of a chemical reaction
not used up over the course of the reaction
state the colours of flames observed when lithium, sodium and potassium burn in oxygen
crimson-red : Li
yellow-orange: Na
lilac: K
describe the properties of noble gases
discuss the trends in properties down the group
non-metals, gases, low boiling point, unreactive (full outer shell so don’t easily accept or lose electrons)
boiling point increases down the group, as atoms get heavier
