Chemistry - Trends in the Periodic table 2 Flashcards Part 2

The halogens

valency 1

have seven electrons in their outer shell and are very reactive.They become less reactive going down the group. (form diatomic molecules - two atoms joined by a covalent bond)

They do not satisfy the octet rule - they have seven electrons in their valence shell. In Order to satisfy the octet rule, they gain one electron when they react and form a momonegative ion

the atomic radius increases

van der waals

halogen molecules are non-polar - have weak van der waals forces between their molecules - have low boiling points.

As the molecules mass increases, the strnght of the intermolecular forces increases.

Fluorine (F2) and Chlorine (Cl2) are gases at room temperature

Bromine (Br2) is a volatile liquid at room temperature

Iodine (I2) is a volatile solid at room temperature

the nobel gasses

valency of 0

they have eight electrons in their outer shell - this is a stable arrangement of electrons do not gain, lose, or share electrons - already satisfy the octet rule. Makes then very inert and safe to use.

half the distance between the nuclei of two atoms of the same element joined by a single covalent bond

Atomic radii values decrease going across a period (Atoms get smaller)

The effective nucler charge increases- more protons in the nucleus means there is an increasng attraction between the nucleus and electrons in the outer shell, and the atom is being "pulled smaller"

atomic radii values increase going down a group (atoms get larger). An additional shell of electrons is added on

The noble gasses satidy the octet rule- they do not gain, lose or share electrons so do not form bonds with other elements

the measure of reltive attraction an atom has for a shared pair of electrons in a covalent bond

electtronegativity calues increase going across a period.

1. The atomic radius decreases - pair of electrons in the covalent bond become closer to the postive nuclear charge

2. the effective nuclear charge increases- more protons in the nucleus means there is an increasing attracting between the nulceus and electrons in the covalent bond.

Electronegativity values decrease going down a group.

1 the atomic radius increases- pair of electrons in the covalent bond become futher from the postive nuclear charge.

No increase in effective nuclear charge due to extra shell- electrons in covalent bond are more shielded from the nucleus.

the noble gases satisfy the octet rule- they do not gain, lose, or share electrons so do not form bonds with other elements.

the minimum energy required to remove the most loosely boind electron from an atom or ion

the minimim energy required to remove the most loosely bounf electron from a netural gaseous atom in the ground state

K(g) ----> K+(g) + e-

K+(g) ---> K2+ (g) + e-

K2+(g) ---> K3+ (g) + e-

kilojoules per mole

the first ionisation energy values generally increase going across a period.

atomic radius decreases - the electron being removed becomes closer to the postive nuclear charge.

The effectve nuclear charge increases - more protons in the nucleus means there is an increasing attraction between the nucleus and the electron being removed.

First ionisation energy values decrease going down a group.

The atomic radius increases - electrons removed futher from the postive nuclear charge.

No increase in effecive nuclear charge due to an extra shell- most loosley bound electron is screened from the nucleus

small decreases in ionsiation energies are due to electrons being removed from full sublevels, and half- full sublevels will require energy as these are high stability configurations

it takes substiantially less energy to remove an electron from a shell futher from the nucleus - this explains

the minium energy required to remove the most loosly bound electron from a postive ion

1- the second electron is being removed from a postive ion- the effective nuclear charge has incresed so there is greater sttraction between the electron being removed and the nucleus

2-The atomic radius has decreased in the postive ion - the second electron being removed is closer to the postive nuclear charge

when attemption to remove an electron from a new energy level, a substantially higher amount of amount of energy is required.

looking at the number of substantial increases in ionisation energy will show how many energy levels are occupies by electrons in the atom

line emission spectra