Chapter 7

Arranged elements in order of atomic mass Aligned elements in groups with similar properties Swapped elements and left gaps Predicted the properties of missing elements

The elements are arranged in vertical columns Same number of outer shell electrons

The elements are arranged in horizontal rows Number of the highest energy electron shell in the elements atom

A repeating trend in properties of the elements across each period

Each period starts with an electron in a new highest energy shell S subshell fills with 2 electrons P fills with 6 Group 4 3D subshell fills with 5

Elements in each group have atoms with the same number of electrons in each sub shell Same chemical properties

Divides elements corresponding to their highest energy sub shell

Measures how easily an atom loses electrons to form positive ions

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

Atomic radius Electron shielding Nuclear charge

The greater the distance between the nucleus and outer electrons the less the nuclear attraction the easier it is to lose an electron

The more protons there are Te greater the attraction between the nucleus and outer electrons Harder to lose electrons

Inner shell electrons repel outer shell electrons = shielding effect Reduces the attraction between the nucleus and outer electrons

Removed from positive ion, more protons than electron Greater pull on electrons from nucleus Less shielding and repulsion from other electrons so held more closely Large jump in ionisation energy across shells because - less shielding

The number of electrons in the outer shell The group of the element The identity of the element

General increase in first ionisation energy Sharp decrease between the end of one period and the start of another

FIE decreases down a group Atomic radius increases Shielding increased Nuclear attraction on outer electrons decreases

General increase of FIE Nuclear charge increases Same shell - same shielding Nuclear radius decreases Nuclear attraction increases

The start of filling the 2p subshell 2p subshell in boron has a higher energy than the 2s subshell in beryllium Therefore 2p electron is easier to remove than one of the 2s electrons in beryllium

Due to the existence of subshells, their energies, and how they fill with electrons

Phosphorous has 3 electrons in the 3p subshell (1 in each) Sulfur has 4 electrons in the 3p subshell (2 paired in one orbital, 1 in each of the other 2) The paired electrons in sulfur repel each other Making it easier to remove one of these electrons than an unpaired one

Elements near the metal/non metal divide

Strong electrostatic attraction between positive cations and negative delocalised electrons Billions of metal atoms held by metallic bonding to form giant metallic lattices

Strong metallic bonds High electrical conductivity High mp bp