Periodic trends

Anions have a negative charge and are larger than the atoms from which they formed

The group with the highest ionization energy is Group 18

Cations have a positive charge and are smaller than the atoms from which they formed

Electronegativity decreases down a group

number of protons increase across a period

Ionization energy decreases down a group

The energy to remove an electron is ionization energy

Atomic radius decreases across a period and increases down a group

Electronegativity increases across a period

Ionization increases across a period

Least electronegative elements are alkali metals

The measure of the attraction that an atom has for electrons involved in chemical bonds is known as electronegativity

The most active metals are located in the lower left hand corner of the periodic table
The elements with the largest atomic radii are found in the  lower left-hand corner of the periodic table

atomic mass - the number of protons = neutrons

noble gases have no electronegativity because they have a full valence shell

Low first ionization energies are characteristic of metals, particularly alkali metals

The elements with the largest atomic radii are found in the


WHY does the atomic radii from left to right become smaller?

  • As more protons are added, electrons are added as well, causing attraction to become stronger between the protons and electrons.

  • effective nuclear charge is increased

Within a group, the ionization energy changes because

Explain how the atomic radius of an element is related to its chemical reactivity and ionization energy.

  • Increasing atomic radii indicates increasing chemical reactivity due to decreasing ionization energy.


    In the Modern Periodic Table, the elements are arranged in order of

  • Atomic number

  • Shielding: when inner electrons block the positive charge of the nucleus from reaching the outer electrons. This makes the outer electrons feel less attraction to the nucleus, which means it takes less energy to remove them.

Atomic radii generally decrease from left to right. As you move across a period, more protons are added to the nucleus, which increases the positive charge and pulls the electrons closer, reducing the size of the atom.

the closer to 8 valence electrons means higher Ionization energy

The more protons the stronger the effective nuclear charge