Elements and the periodic table Flashcards
Matter
Anything that occupies space and has a mass
Solids
Fixed 3D lattice
Attraction between particles very strong- high MP and BP
Only vibrate- don’t move out of fixed positions
Liquids
Particles disordered- collide into each other and walls of the container
volume remains constant
attraction between particles weaker than in solid state
Gases
Particles far apart and disordered
Collide into each other and move until they collide with the walls of the container
volume is not constant
Attraction between particles weakest
Mass
Measure of the quantity of matter in an object, regardless of the gravity force
Weight
Force that gravity exerts on an object
Substance
Form of matter with constant composition, distinct properties and can write a chemical formula
Mixture
combination of two or more substances
no constant composition
cannot write a chemical formula
Element
Substance made of only one type of atom
Compound
Substance made of two or more different types of atoms
Chemical identity of an atom
Determined solely by its atomic number
Isotopes
Atoms that have the same atomic number but different mass numbers
Protons an electrons determine chemical properties of an element
Neutrons dont take part in chemical reactions
Isotope similarities
Atomic number
Chemical properties
Number of electrons
Isotope differences
Mass number
Number of neutrons
Stability of nucleus
MP and BP table
Solid Liquid Gas
MP + - -
BP + + -
Hydrogen spectra
Neils Bohr’s shell model
Visible hydrogen spectrum consists of four lines (red, green, blue and violet) observed by passing an electric current through hydrogen gas
electrons move around nucleus at specific energy levels
can transition from a lower energy level to a higher energy level by absorbing energy
higher energy electron- excited state
excited electron is unstable and falls back to ground state, emitting the absorbed energy
This energy corresponds to the coloured lines on the spectrum
electron in lowest possible energy shell- ground state
Schrodinger
Quantum mechanical model
electrons form a cloud of negative charge around the nucleus
shells, sub shells, orbitals
Valence electrons
involved in chemical reactions because they are unstable
Octet rule
Outermost shell can never contain more than 8 electrons regardless of the maximum possible number for that shell
Max no. electrons in shell
2
2n
Pauli principle
Gives the number of electrons in any orbital
An atomic orbital can hold a maximum of two electrons
4s and 3d
Electrons occupy the lowest energy sub-shell in an atom first
As shells move away from the nucleus, they get closer to each other
As they get further away, in some cases, the sub shell of one shell are higher in energy than the sub shell of the next shell
3d sub shell is higher in energy than 4s subshell so 4s must be filled first
Ions
Atoms have either gained or lost electrons and are no longer neutral but have an electrical charge
Cations
Lost electrons
Positively charged
Metals
Anions
Gained electrons
Negatively charged
Non-metals
Dalton
Atomic theory
- All matter is composed of tiny, indivisible particles called atoms (SUBATOMIC PARTICLES)
- All atoms of the same element are identical in mass and properties (ISOTOPES)
- Compounds have atoms of different elements combined in whole number ratios
- Atoms are neither destroyed or created in chemical reactions
- most stable compounds of two elements contain atoms in a one-to-one ratio (CAN BE ANY RATIO)
Lavoisier
Law of conservation of mass
During a chemical reaction, the mass of reactants is equal to the mass of the products
Mendeleev
Early periodic table
Arranged in order of increasing atomic masses
Groups of elements had similar properties
Gaps were left for unknown elements, predicted their properties
Modern periodic table
Discrepancies were resolved
Elements arranged according to increasing atomic number
Elements classified according to atomic numbers and electrons configurations
Same group, same number of valence electrons
Same period, same number of occupied electron shells
s-block
2 columns- because s sub shell has one orbital and a maximum of two electrons
I alkali metals
II alkaline earth metals
highest energy electron is in s-sub shell
p-block
6 columns- because p sub shell has 3 orbitals and a maximum of 6 electrons
VII halogens
VIII noble gases
highest energy electron is in p-sub shell
d-block
10 columns- because d sub shell has 5 orbital and a maximum of 10 electrons
transition metals
highest energy electron is in d-sub shell
f-block
14 columns- because f sub shell has 7 orbital and a maximum of 14 electrons
4f- lanthanides
5f- actinides
highest energy electron is in f-sub shell
Nuclear charge
equal to atomic number
Lithium- nuclear charge is +3 but the full force of this charge is partially offset by the mutual repulsion of the two 1s electrons
the 2s electron is shielded from the nucleus by the other electrons
Electron shielding
Electrons in a given shell are shielded by electrons in inner shells but not by those in outer shells
Inner filled shell electrons shield outer electrons more effectively than electrons in the same sub shell shield each other
Core charge
Effective charge of the nucleus that is experienced by the outer shell electrons
inner shell electrons shield the protons in the nucleus so the outer shell electrons experience reduced attraction
core charge= group number= atomic no.- inner full shell electrons
Atomic radius
Distance from nucleus to valence shell
Metallic character
Tendency of an atom to lose electrons, and form a cation
Ionisation energy
The minimum energy required to remove an electron from a gaseous ground state atom or ion
Takes less energy to remove the first electron from the ground state atom and more energy is required for remaining electrons from resulting ion
Why does it take less first IE for first electron?
Electron shielding results in a weaker attraction of the nucleus for each electron
When first electron is removed, fewer electrons are present so there is less shielding and electrons feel larger effect of the nuclear charge
Highest and lowest first IE
Highest= noble gases lowest= group one
Size of cations
Cation is smaller than neutral atom because cation’s valence shell is pulled towards nucleus with more effective nuclear charge
Size of anion
Anion is bigger than neutral atom because anion valence shell is pulled towards the nucleus with less effective nuclear charge
Metal reacitivty
depends on first ionisation energy as metals lose electrons in chemical reactions
Non-metal reactivity
Depends on electronegativity as non-metals gain electrons in chemical reactions
Chromium
4s1 3d5
Copper
4s1 3d10
Chromium and copper exceptions
Because the most stable electron configurations are when the sub-shell is half or completely filled with electrons, to minimise electron repulsion, the subshell is half-filled first
Electron transfer from 4s to 3d
Possible because energy of 4s and 3d are almost the same
Electron transfer increases the stability of the atom
Only occurs in the d-block, when d sub shell is almost half or completely full
