periodicity Flashcards
Who created the periodic table arrangement?
Dmitri Mendeleev
a row
period
a column
group
noble gases
unreactive non-metals, gases at room temperature, monatomic
halogens
very reactive non-metals, coloured
alkali earth metals
fairly reactive metals
alkali metals
very reactive metals, usually stored under oil to prevent reaction with oxygen and water vapour in the air
transition metals
metals often used as catalysts
melting point
increases across a period and decreases down a group
boiling point
increases across a period and decreases down a group
density
increases across a period, decreases down a group
covalent radius
a measure of the size of an atom, half the distance between the nuclei of 2 of its bonded atoms
covalent radius across a period
decreases due to increased nuclear charge of the atoms, energy levels of electrons more strongly attracted to the positive nucleus
covalent radius in a group
increases as there is an increase in the number of electron shells which makes the atom bigger
ionisation energy
the first ionisation energy of an element is the energy required to remove one mole of electrons from one mole of gaseous atoms.
ionisation energy across a period
increases, more energy required ro remove electron as there is an increased nuclear charge, also atoms getting smaller therefore electron is closer held to the nucleus.
ionisation energy down a group
decreases, less energy required to remove outer electron as it is further from the nucleus, also screening effect as more shells of electrons between the electron and nucleus.
second ionisation energy
the energy required to remove the second mole of electrons
electronegativity
a measure of the attraction an atom has for bonding electrons (i.e. how tightly the atom holds on to bonding electrons)
electronegativity across a period
increases, increasing nuclear charge pulls electrons closer to nucleus and greater ability to share electrons, smaller radius means outer electrons are more strongly held, more energy required
electronegativity down a group
decreases as increasing number of electron shells makes the atom bigger, increased shielding means outer electrons are less strongly held, less energy required
