Atomic Structure And The Periodic Table Flashcards
What are all substances made from?
Atoms
What is an atom?
The smallest part of an element that can exist
What is the radius of an atom?
0.1 nm (nanometres) (1 x 10^-10 m), it is very small
What is the radius of the nucleus?
1 x 10^-15 m (1/10000th of the radius of an atom)
Where is most of the mass in an atom located?
In the nucleus
What can elements be represented as?
Symbols
How many elements are there?
About 100
Where are elements shown?
Periodic table
What is a compound?
Two or more different atoms chemically joined together in fixed proportions
How can compounds be separated into their elements?
By chemical reactions
Are the properties of a compound the same as the elements they are made from?
No
What is a mixture?
Two or more elements or compounds not chemically bonded together, the chemical properties of each substance in the mixture are unchanged
What are 5 ways to separate a mixture?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography
Why are the techniques used to separate mixtures described as physical processes?
As mixtures contain two or more elements or compounds not chemically combined
Why is a lid used in chromatography?
Stops solvent evaporating
How does filtration work?
Pass through filter paper, liquid passes through, insoluble particles get caught by the filter paper
How do you carry out crystallisation?
Evaporation dish and heat source. Filter crystals out of the solution
How can you get sand and salt from a mixture of the two?
Dissolve in water, salt is soluble, sand isn’t. Filter to remove sand, then use crystallisation
What two processes are involved in distillation?
Evaporation and condensation
Where is the hottest part in fractional distillation?
The bottom
What property must the mixture have to be able to separate by fractional distillation?
Each part of the mixture must have different boiling points
What is an element?
A substance made up of only one type of atom
What is a molecule?
Two or more atoms joined together e.g. O2, Cl2, H2O, CO2
Where are the reactants found in an equation?
Left hand side
Where are the products found in an equation?
Right hand side
What is distillation?
The separating of a liquid using evaporation and then condensation
What is fractional distillation?
A method used to separate two or more liquids
What is chromatography?
A method used to separate the coloured compounds in a mixture
What is filtration?
A method used to separate an insoluble solid from a liquid
What is crystallisation?
A way to separate a dissolved solid from a solution by evaporation to leave crystals of the solid.
What sub atomic particle was discovered first?
Electron.
Before electrons were discovered, were atoms thought to be divisible?
No.
Before electrons were discovered, atoms were thought to be what?
Tiny spheres.
What model did the discovery of the electron lead to?
Plum pudding model.
What was the plum pudding model?
That the atom was a ball of positive charge with negative electrons embedded in it.
What model replaced the plum pudding model?
Nuclear model.
What experiment led to the idea that the mass of the atom was concentrated in the centre?
Alpha scattering experiment.
What would happen with the alpha particle experiment if the plum pudding model was correct?
Expect particles to pass straight through or slightly deflected.
What was observed in the alpha scattering experiment?
Alpha particles were fired at a thin sheet of gold. Most of the particles passed through, some deflected more than expected, and very few deflected backwards.
What charge are alpha particles?
Positively charged.
Explain the observations of the alpha scattering experiment.
Most of the particles passed through = atom is mostly empty space. Some deflected more than expected = alpha particles hit a positively charged centre and repelled. Very few deflected backwards = alpha particles hit a concentrated mass.
Describe the nuclear model.
Nuclear model has a positively charged nucleus where most of the mass is concentrated and most of the atom is empty space.
Who led to the idea that electrons are in orbitals/shells?
Niels Bohr.
What order were the sub atomic particles discovered?
Electron, proton, neutron.
Who provided evidence for the existence of neutrons within the nucleus?
Chadwick (about 20 years after the nucleus idea was accepted).
What are the differences between the plum pudding model and the nuclear model?
Plum - single ball of positive charge spread throughout, electrons embedded, no nucleus, no neutrons; nuclear - positive centre/nucleus, electrons in fixed positions, has a nucleus, has neutrons.
What did Bohr suggest about the arrangement and movement of electrons?
Electrons orbit the nucleus in shells that are a fixed distance from the nucleus. Electrons can only be found in these shells.
What particle was discovered as the nucleus was found to be positive?
Proton.
Name the three sub atomic particles.
Proton, neutron & electron.
What is the relative charge of a proton?
1+.
What is the relative charge of a neutron?
0.
What is the relative charge of an electron?
1-.
Why do atoms have no overall electrical charge (are neutral)?
The number of positive protons equals the number of negative electrons so charges cancel out.
What does the atomic number tell you?
Number of protons.
What makes an atom of an element the element it is?
The protons, e.g. If an atom has 8 protons, it must be oxygen.
What makes atoms of elements different to each other?
They have a different number of protons.
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
Very small
What is mass number?
The sum of the protons and neutrons in an atom.
What is an isotope?
The same element but with the same number of protons but different numbers of neutrons e.g. C-12 and C-13.
Why is the relative atomic mass of chlorine not a whole number?
Has more than one isotope.
How do the chemical properties of an isotope differ?
Doesn’t - has have the same number of electrons.
How do you work out the number of protons?
Use the atomic (proton) number.
How do you work out the number of electrons in an atom?
Same as the protons.
How do you work out the number of neutrons?
Mass number - atomic number.
What is relative atomic mass?
The average value that takes account of the abundance of the isotopes of an element.
How do you calculate relative atomic mass of an element given the percentage abundance of its isotopes?
(mass x abundance) + (mass x abundance) + ….
relative atomic mass = (35 x 75) + (37 x 25) / 100 = 35.5
What do the electrons occupy in an atom?
The lowest available energy levels.
How many electrons are there found in shells 1, 2 & 3?
2, 8, 8.
What sub atomic particle is involved in bonding (chemical reactions)?
Electrons.
What holds atoms of elements together in compounds?
Chemical bonds.
How were early periodic tables arranged?
By atomic weights (as protons, neutron and electrons were not discovered).
What did Newland do wrong?
Put more than one element in a box and followed a strict order of atomic weight. His pattern eventually broke down.
What is the name of the scientist who first published the periodic table?
Dmitri Mendeleev.
What did Mendeleev do to solve the problem of elements not in the correct groups?
He left gaps for undiscovered elements and was able to predict the properties of these.
How is the modern periodic table ordered?
In order of atomic number (protons).
What are elements with similar properties called?
Groups (columns).
What do all elements in the same group have in common?
The same number of electrons in their outer shell.
How is the modern periodic table arranged?
Atomic number (protons) with elements in the same group as their outer number of electrons.
What is the name given to the columns on the periodic table?
Group.
What is the name given to the rows of the periodic table?
Periods.
What does the group number of an element tell you?
The number of electrons in its outer shell/energy level.
What does the period number of an element tell you?
Number of energy levels the atom has.
How many groups are there on the periodic table?
8.
How are the metals and non-metals arranged in the periodic table?
Metals are on the left hand side and non-metals on the right.
What is an ion?
A charged particle.
What types of ions do metals form?
Positive, as they lose electrons to get a full outer shell.
What types of ions do non-metals form?
Negative, as they gain electrons to get a full outer shell.
What elements are found in the block of the periodic table between groups 2 & 3?
Transition metals.
What are the elements in group 0 called?
Noble gases.
Why are Noble gases unreactive/inert?
As they have a full outer shell so their atoms have stable electron arrangements (He-2, all others-8).
What happens to the boiling point of the Noble gases as you go down the group?
Increases, as relative atomic mass increases so stronger intermolecular forces.
What does monoatomic mean (Noble gases)?
Exist as atoms.
What are the elements in group 1 called?
Alkali metals.
How many electrons do all group 1 elements have in their outer shell?
1.
Why do the metals in group 1 have similar properties?
All have 1 electron in their outer shell.
What happens to the melting point as you go down group 1?
Decreases.
What happens to the reactivity of the group 1 metals as you go down the group?
Increases.
Why do the alkali metals become more reactive as you go down the group?
Increase in number of electrons/electron shells, outer electron is further from the nucleus so is less attracted to the positive nucleus, so easier to lose an electron.
Give three characteristics of alkali metals.
Metals, soft, highly reactive.
What are the products when a group 1 metal reacts with water?
Metal hydroxide and hydrogen.
What is the word equation for the reaction of sodium with water?
Sodium + water → sodium hydroxide + hydrogen.
What is the balanced symbol equation of sodium with water?
2Na + 2H2O → 2NaOH + H2.
What observations do you see when an alkali metal reacts with water?
Alkali metals float on water = less dense than water. Alkali metals fizz = hydrogen gas released. Universal indicator (if added) goes purple = alkali produced aka metal hydroxide. Metal dissolves = metal reacting to produce metal hydroxide (aq).
Reactions become more vigorous as go down group 1
What is observed when lithium reacts with water?
Floats, moves on the surface, fizzes
What is observed when sodium reacts with water?
Floats, forms a ball, moves on the surface, fizzes, a yellow flame
What is observed when potassium reacts with water?
Floats, forms a ball, moves on the surface, fizzes, a lilac flame
What is formed when alkali metals react with oxygen?
Metal oxide
What is the word equation for the reaction of sodium with oxygen?
Sodium + oxygen → sodium oxide
What is the symbol equation for the reaction of sodium with oxygen?
4Na + O2 → 2Na2O
What observations do you see when lithium reacts with oxygen?
Red-tinged flame, bright flame in oxygen, white solid formed
What observations do you see when sodium reacts with oxygen?
Brighter flame in oxygen, white solid formed, lilac flame
What observations do you see when potassium reacts with oxygen?
Even brighter flame in oxygen, white solid formed
What is formed when alkali metals react with chlorine?
A metal halide is formed e.g. Sodium chloride
What is the word equation for the reaction of sodium with chlorine?
Sodium + chlorine → sodium chloride
What is the symbol equation for the reaction of sodium with chlorine?
2Na + Cl2 → 2NaCl
What observations do you see when group 1 elements react with chlorine?
Bright flame & White solid
What are the elements in group 7 called?
Halogens
How many electrons do all group 7 elements have on their outer shell?
7
What state is chlorine at room temperature and its colour?
Yellow/green gas
What state is bromine at room temperature and its colour?
Brown liquid
What state is iodine at room temperature and its colour?
Purple solid
Three properties of the halogens are?
Non-metals, very reactive, diatomic (exist as molecules), melting points and boiling points increase down the group
What is the charge on a halide ion?
-1, as lose one electron to get a full outer shell
What happens to the reactivity of the group 7 halogens as you go down the group?
Decreases
Why do the halogens become less reactive as you go down the group?
Increase in number of energy levels, outer shell of electrons are further from the nucleus
What sort of compounds do halogens form with other non-metals?
Covalent
What sort of compounds do halogens form with metals?
Ionic
What sort of molecules do all halogens form?
Diatomic, go round in pairs
What is a displacement reaction?
When a more reactive element displaces a less reactive element in a compound
What is a word equation to show the displacement reaction between chlorine and sodium bromide?
Chlorine + sodium bromide → bromine + sodium chloride
What is a symbol equation to show the displacement reaction between chlorine and sodium bromide?
Cl2 + 2NaBr → Br2 + 2NaCl
Where are the transition metals found in the periodic table?
In the centre, between group 2 and group 3
What properties are different in transition metals compared to alkali metals?
Higher melting point, higher density, stronger, harder, less reactive
How does the reactivity of transition metals compare to alkali metals?
Less reactive
What are the properties of transition metals?
Can form different charged ions, form coloured compounds, useful as catalysts
What property of transition metals is an important industrial use?
Used as catalysts which speed up reactions
