Trends in Atomic Numbers 1 to 30

When studying elements with atomic numbers 1 to 30, you should focus on the following periodic trends:

• Atomic Radius: Generally decreases across a period (left to right) and increases down a group.
• Ionization Energy: Generally increases across a period and decreases down a group.
• Electronegativity: Generally increases across a period and decreases down a group.
• Electron Affinity: Generally becomes more negative across a period and less negative down a group.

These trends are essential because they help predict the chemical behavior of elements. For example, elements with high electronegativity, like Fluorine (atomic number 9), are highly reactive non-metals, while those with low ionization energy, like Sodium (atomic number 11), are highly reactive metals.