Periodic trends are important for understanding how elements behave based on their properties.

1. Atomic Radius:

• The size of an atom, called the atomic radius, gets smaller as you move from left to right across a row of the periodic table.
• For example, Lithium has an atomic radius of 186 picometers (pm), while Neon is much smaller at 70 pm.
• However, as you go down a column, the atomic radius increases.
• For instance, Hydrogen is 74 pm, but Cesium is much larger at 262 pm.

2. Electronegativity:

• Electronegativity is a measure of how strongly an atom attracts electrons.
• This value usually gets higher as you move from left to right across a row.
• For example, Francium has an electronegativity of 0.7, while Fluorine has a high value of 4.0.
• On the other hand, electronegativity decreases as you go down a column.
• For example, Fluorine is at 3.2, but Cesium is at 0.7.

3. Ionization Energy:

• Ionization energy is the energy required to remove an electron from an atom.
• This value usually increases as you move from left to right across a row.
• For example, the ionization energy goes up by 1.62 electron volts (eV) from Sodium to Chlorine.
• In contrast, ionization energy tends to decrease as you go down a column.
• For instance, Potassium has an ionization energy of 1.0 eV, but Cesium's is only 0.5 eV.

These trends help scientists predict how elements will react in chemical reactions.