Question

element name of element valence electrons e - gained or lost to form octet (8 ve) symbol of ion anion or cation o se ba br li part 3: periodic trends 22. what happens to the size of the atoms as you move across a period? 23. what happens to the ionization energy as you move across a period? 24. what happens to the electronegativity as you move across the periodic table? 25. what happens to the size of atoms as the atomic number within a group increases? 26. what happens to the ionization energy of atoms as the atomic number within a group increases? 27. what happens to the electronegativity of atoms as the atomic number within a group increases? 28. why is there no electronegativity value listed for the noble gasses? 29. when an atom becomes a cation does it get larger or smaller? why?

Explanation:

Step1: Fill in the table for elements

• O (Oxygen): Name is oxygen. It has 6 valence electrons. To form an octet, it gains 2 electrons. The ion symbol is $O^{2 - }$ and it is an anion.
• Se (Selenium): Name is selenium. It has 6 valence electrons. To form an octet, it gains 2 electrons. The ion symbol is $Se^{2 - }$ and it is an anion.
• Ba (Barium): Name is barium. It has 2 valence electrons. To form an octet, it loses 2 electrons. The ion symbol is $Ba^{2+}$ and it is a cation.
• Br (Bromine): Name is bromine. It has 7 valence electrons. To form an octet, it gains 1 electron. The ion symbol is $Br^{-}$ and it is an anion.
• Li (Lithium): Name is lithium. It has 1 valence electron. To form an octet, it loses 1 electron. The ion symbol is $Li^{+}$ and it is a cation.

Step2: Answer periodic - trend questions

• 22: As you move across a period, the size of the atoms decreases. This is because the number of protons increases, increasing the nuclear charge, which pulls the electrons closer to the nucleus.
• 23: The ionization energy increases as you move across a period. The increased nuclear charge makes it harder to remove an electron.
• 24: The electronegativity increases as you move across the periodic table. The increased nuclear charge allows the atom to attract bonding - electrons more strongly.
• 25: As the atomic number within a group increases, the size of atoms increases. This is due to the addition of new electron shells.
• 26: As the atomic number within a group increases, the ionization energy decreases. The outermost electrons are further from the nucleus and are more easily removed.
• 27: As the atomic number within a group increases, the electronegativity decreases. The increased atomic size reduces the ability of the nucleus to attract bonding - electrons.
• 28: Noble gases have no electronegativity value listed because they have a full valence shell and are chemically inert. They do not readily attract electrons to form compounds.
• 29: When an atom becomes a cation, it gets smaller. This is because the loss of electrons reduces electron - electron repulsion, and the remaining electrons are pulled closer to the nucleus.

Answer:

Element	Name of element	Valence electrons	e - gained or lost to form octet (8 VE)	Symbol of ion	Anion or cation
Se	Selenium	6	Gains 2	$Se^{2 - }$	Anion
Ba	Barium	2	Loses 2	$Ba^{2+}$	Cation
Br	Bromine	7	Gains 1	$Br^{-}$	Anion
Li	Lithium	1	Loses 1	$Li^{+}$	Cation
22	The size of the atoms decreases.
23	The ionization energy increases.
24	The electronegativity increases.
25	The size of atoms increases.
26	The ionization energy decreases.
27	The electronegativity decreases.
28	Noble gases have a full valence shell and are chemically inert.
29	It gets smaller because the loss of electrons reduces electron - electron repulsion and the remaining electrons are pulled closer to the nucleus.