The correct option is **C. electropositive character of elements increases**. ### Detailed Explanation: 1. **Understanding the Periodic Table**: - The periodic table is organized in such a way that elements are arranged by increasing atomic number from left to right. Each element has a unique atomic number, which corresponds to the number of protons in its nucleus. 2. **Analyzing Each Statement**: - **A. Atomic number of elements increases**: This statement is true. As you move from left to right across a period, each subsequent element has one more proton (and one more electron) than the element before it. For example, moving from sodium (Na, atomic number 11) to magnesium (Mg, atomic number 12), the atomic number increases. - **B. Atomic mass of elements increases**: This statement is also true. Generally, as you move from left to right, the atomic mass tends to increase because the number of protons and neutrons in the nucleus increases. For instance, sodium has an atomic mass of approximately 23 u, while magnesium has an atomic mass of about 24.3 u. - **C. Electropositive character of elements increases**: This statement is **not true**. Electropositive character refers to the tendency of an element to lose electrons and form positive ions (cations). As you move from left to right across a period, elements become less electropositive. For example, alkali metals (like sodium and potassium) on the left are very electropositive, while nonmetals (like chlorine and oxygen) on the right are not. Thus, the electropositive character decreases, making this statement incorrect. - **D. Electronegative character of elements increases**: This statement is true. Electronegativity is the tendency of an atom to attract electrons in a chemical bond. As you move from left to right, elements become more electronegative. For example, fluorine (F) is highly electronegative, while lithium (Li) is not. This trend is due to the increasing nuclear charge, which attracts electrons more strongly. 3. **Why Other Options Are Correct**: - **Option A** is correct because the atomic number increases with each element. - **Option B** is correct because atomic mass generally increases as you move across a period. - **Option D** is correct because electronegativity increases due to the increasing effective nuclear charge that attracts electrons more strongly. ### Common Pitfalls: - Students often confuse electropositivity with electronegativity. Remember that electropositivity refers to the ability to lose electrons, while electronegativity refers to the ability to attract electrons. - It’s important to remember that trends in the periodic table are not absolute; there are exceptions, especially with transition metals and heavier elements. ### Revision Summary: - As you move from left to right in the periodic table: - Atomic number increases (True). - Atomic mass generally increases (True). - Electropositive character decreases (False). - Electronegative character increases (True). Understanding these trends is crucial for mastering concepts in chemistry and predicting the behavior of elements in reactions.