3. Periodicity Flashcards
according to which property are elements arranged in the PTE
their atomic number/number of protons/Z
metals
- electrons
- charge of ions
- conductivity
- form
- melting point/boiling point
- lose electrons
- positive charge (cations)
- good heat and electricity conductors (in solid state and when liquid/molten)
- malleable and ductile
- high melting and boiling point (hard to break metallic bonds - strong intermolecular bonds)
non-metals
- electrons
- charge of ions
- conductivity
- form
- melting point/boiling point
- gain electrons
- negative charge (anions)
- non-conductors/isolators of both heat and electricity
- brittle solids
- low melting point - many in gaseous state at room temperature (sublimation means that the boiling point is very low)
octet rule
elements usually react in such a way as to obtain the electron configuration of the noble gas closest to them in the PTE
isoelectric
ions of different elements that have the same number of electrons
trends in the PTE
1|atomic radius
2|electron affinity
3|size of ions
4|ionization energy
5|electronegativity
atomic radius
size of an atom
increases down and to the left
electron affinity
measure of the energy change when an electron is added to a neutral atom to form a negative ion (affinity to gaining electrons)
absolute value increasing up and to the right
size of ions
cations<atoms<anions - number of protons stays the same but number of electrons increases - weaker attraction force, further away from the nucleus - number of shells may change as well
ionization energy
the energy needed to remove one mole of electrons from one mole of an isolated, gaseous atom/ion
increasing up and to the right
electronegativity
chemical property that describes the ability of an atom (or a functional group) to attract electrons toward itself in a covalent bond (bond not equally shared)
increases up and to the right
the smaller the atomic radius the greater the electronegativity
FONCl (4 most electronegative elements)
alkali metals
- I. group (H excluded)
- soft elements
- rigorous reaction with water and air
- reactivity increases down the group (because atomic radius gets greater and so electrons are more easily lost because the attraction force is smaller)
- strong reducing agents - small nuclear charge so they can easily lose e- (want to get to noble gas e- configuration)
- melting point: increases up the group (inverse proportional with atomic radius - easier to break them apart because their nuclei are further apart and the attraction force is weaker - metallic bond)
- when recating with halogens, produce salts (vigorous reaction)
halogens
- VII. group
- diatomic molecules
- reactive elements - only have to gain one electron to achieve n-g- configuration
- reactivity increases up the group (atomic radius gets larger so it’s harder to gain electrons because the attraction force of the nucleus is lesser)
- strong oxidizing agents (proportional to reactivity) - want to gain electrons
F2>Cl2>Br2>I2 - melting point: increases down the group (proportional with molar mass) - intermolecular forces in covalently bonded compounds: Van der Waals bond strength is proportional with molar mass
- when reacting with alkali, produce salts (vigorous reaction)
- presence of halogens can be detected by placing silver nitrate solution
why do C and Si peak on the melting point graph and why is C melting point greater than Si m.p.
because they have giant covalent structures that are difficult to break (require a lot of energy)
C>Si because it has one less shell and therefore a smaller radius, greater attraction force between nucleus and shells and more E is needed to break the bonds
metalloids conductivity
semi-conductors
metallic oxides
- ionic compounds
- high melting and boiling points
- conduct electricity when molten/aqueous but not solid
- when reacted with water form basic solutions
