Complete each of the statements a to d using 1, 2, or 3: 1. decreases 2. increases 3. remains the same Going from left to right across Period 4, d. the number of valence electrons

Periodic trends refer to the predictable patterns observed in the properties of elements as you move across a period or down a group in the periodic table. These trends include atomic radius, ionization energy, electronegativity, and the number of valence electrons. Understanding these trends is essential for predicting how elements will behave in chemical reactions.

Valence electrons are the electrons in the outermost shell of an atom that are involved in forming chemical bonds. The number of valence electrons determines an element's reactivity and its ability to bond with other elements. In Period 4, elements gain valence electrons as you move from left to right, which influences their chemical properties.

Period 4 of the periodic table includes elements from potassium (K) to krypton (Kr). As you progress across this period, the atomic number increases, leading to an increase in the number of protons and electrons. This results in a corresponding increase in the number of valence electrons, which is crucial for understanding the chemical behavior of these elements.