Trends in the Periotic table

Half the distance between the nuclei of two atoms of the same element that are joined by a single covalent bond

Value increases going down groups in the periodic table

• each time we move down the periodic table we add an extra energy level further away from the nucleus, making it bigger

• The extra energy levels further away from the nucleus cancels out the positive nuclear charge on the outer electrons

Value decreases going from left to right in the periodic table

• The nuclear charge increases going across the period (more positive charge, as are more protons in the nucleus), which pulls the outer electrons closer to the nucleus

• No increase in screening effect, as the same period has the same outer energy level

Minimum energy required to completely remove the most loosely bound electrom from a neutral gaseous atom in its ground state

• energy that is needed to pull the loosest (furthes away from the nucleus) electron off an atom

Value of the first ionisation energy decreases going down groups in the periodic table

• increasing atomic radius as we go down a group, means that the outermost electron gets further away from the nucleus, making it easier to remove

• Increasing screening effect of the inner electrons as we go down a group also makes the most loosey bound electrom easier to remove

Value of first ionisation energy increases going from left to right

• increasing effective nuclear charge as we go across a period means that the most loosey bond electron gets pulled more strongly by the nucleus as we go across the group

  More energy is then needed to remove the electron

• Decreasing atomic radius means that the most loosey bound electron gets closer to the nucleus of the atom as we go across the period

  This means the nucleus has a stronger pull on the electron, so it becomes more difficult to remove the electron

Atoms whose outermost sublevels is half full or completely full have extra stability. Ionisition energy is particualarly high

Energy required to remove an electron from an ion with one positive charge in gaseuos state

• energy needed to remove the second loosest electron,a fter the loosest already been removed, this can keep going with the third, fourth..

An atom attracted to shared electron in a chemical bond

decreasing going down a group

• increasing atomic radius

• Screening effect of the inner electron increases going down a group, it reduces the pull that the nucleus has on outer electroms involved in bonding

Increases going from left to right

• increasing effective nuclear charge, increases the pull of the nucleus on the outer electrons involved in bonding

• Decreasing atomic radius, nucleus has a stronger pull on the outer bonding electrons

Alkali metals are very reactive because they only have one electron on their outer energy level

Chemical reactivity increase going down

• add extra energy levels from the nucleus away, increases screening effect, outer electron is easier to remove

• Adding extra energy level, increases atomic radius, reducing the pull that the nucelar charge has on the outer electron, making it easier to remove