NY Regents Chemistry Exam June 2022
The graph below represents the atomic radii of the elements in Period 3 on the Periodic Table of the Elements.
54 State the general trend for the atomic radius of the first seven elements in Period 3 when considered in order from left to right. 
The atomic radius increases as we go from right to left and down on the Periodic Table. This fact can be memorized or you can use Table S to find the atomic radius of elements and see what the trend is. We can slo use the graph given.
Answer : The atomic radius decreases from left to right on the Periodic Table
55 State, in terms of valence electrons, why aluminum and sulfur have different chemical properties. 
Elements with the same number of valence electrons have similar chemical properties. Since Aluminum and sulfur have different chemical properties they have different numbers of valence electrons.
Answer: Aluminum and sulfur have a different number of valence electrons.
56 Identify the element in Period 3 that reacts with oxygen to form an ionic compound represented by X in the formula X2O. 
Period 3 is row 3 on the Periodic Table. An ionic compound consists of a metal with a nonmetal. Oxygen is a nonmetal (to the right of the staircase on the Periodic Table). Therefore, we're looking for a metal (left of the staircase). Moreover, for ionic compounds charges get cross multiple to arrive at the formula. The formula is X2O. Oxygen has a charge of -2 which is why we see 2 next to X in the formula. Since Oxygen has 1 next to it (1 is not shown), the charge of X must be +1, which is Group 1 on the Periodic Table.
Answer: Na (sodium )
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