3.1.1 Periodicity Flashcards
periodicity definition
if the elements are arranged in an order the properties of elements would repeat after some period
what does electronic structure determine
the chemical properties of each element
why do elements in the same group have similar chemical properties
they have the same number of electrons on the outer shell
ionisation energy definition
energy needed to remove 1 mole of outermost electrons from one mole of an element in the gaseous state
what holds the electrons in an atom
electrostatic repulsion
from what blocks are electrons lost from first
S and P
what affects the magnitude of the ionisation energy
the number of protons in an atom
1st ionisation energy equation for Na
Na -> Na+ +e-
why does ionisation energy increase as you increase the number of protons
due to the positive charge on the nucleus increasing so the electrons are held tightly so more energy is needed to overcome them
3 factors that affect ionisation energy
atomic radius
nuclear charge
electron shielding
what happens to atomic radius as you go down a group or across a period
as you go down a group it increases
across a period it decreases
what happens to nuclear charge as you go down a group and across a period
increases as there’s more protons in the nucleus
what happens to electron shielding down a group and across a period
increases down a group and remains constant across a period
how does shielding affect the ionisation energy down a group and across a period
increases across a period
decreases down a group
why is the second ionisation energy of an element higher than the first
in the 1st ionisation they lose an electron so there’s less electrons than protons so the electrons are pulled closer to the nucleus so more energy is needed to remove the second electron
successive ionisation energy definition
energy required to remove 1 electron after another
what does the magnitude of the successive ionisation energy tell us
number of electrons in the outer shell
group the element is in
identity of the element
what does the periodic trends in 1st ionisation energy provide evidence for
the existence of shells and sub-shells
ionic bonding definition
metals and non metals losing and gaining electrons to form positive and negative ions held in an ionic lattice by forces of attraction
covalent bonding definition
sharing of electrons to form electrostatic attraction between a shared pair of electrons and nuclei of the bonded atoms
metallic bond definition
metals forming positive ions surrounded by a sea of delocalised electrons
what determines the strength of a metallic bond
charge of the cation
size of cation
number of delocalised electrons
what covalent structure are boron, carbon and silicon
giant
why do giant covalent lattices have high melting points
due to the strong covalent bond requires high amounts of energy to overcome
what makes a high ionisation energy
small radius
greater nuclear charge
less shielding
so makes a high nuclear attraction which requires lots of energy to overcome
electronegativity definition
power of an atom to attract electron density from a covalent bond
why is the 1st ionisation energy of oxygen less than nitrogen
as O has a new pair in the sub-shell so electron pair repulsion increases
why is the first and second ionisation energy of strontium less than those of calcium
they are less than strontium as they have a larger atomic radius which causes increase in shielding they have a high nuclear charge but that’s outweighed by shielding and atomic radius so therefore nuclear attraction is weaker so less energy is required to remove outermost electron
