Question

1. how do you determine the number of valence electrons that an element has?
2. where on the periodic table would you look to find the group number?
3. the text says \the periodic table is like read a book\. why is a book a good comparison

to the periodic table?

1. name some properties of the halogens group.
2. name some properties of the noble gases group.
3. complete the claims and evidence grid to answer the following question:

how many valence electrons does an atom of neon have?
my claim \tmy evidence

1. complete the claims and evidence grid to answer the following question:

how many energy levels does an atom of calcium have?
my claim \tmy evidence

Explanation:

To answer these questions about periodic trends, we analyze each:

Question 9: Determine valence electrons

Valence electrons are determined by an element’s group number (column) on the periodic table. For main - group elements (Groups 1, 2, 13–18):

• Group 1: 1 valence electron.
• Group 2: 2 valence electrons.
• Groups 13–18: Valence electrons = group number - 10 (e.g., Group 14 has 4, Group 17 has 7).

Transition metals (Groups 3–12) have more variable valence electrons (based on electron configurations).

Question 10: Find group number

The group number (vertical column) is labeled at the top of each column on the periodic table. For example, Group 1 (alkali metals) is the first column, Group 18 (noble gases) is the last.

Question 11: Periodic table as a book

A book is a good comparison because:

• Like a book’s pages (organized sequentially), the periodic table’s rows (periods) are ordered by increasing atomic number (left - to - right, top - to - bottom).
• A book has chapters/sections; the periodic table has groups (columns) with elements sharing similar properties (e.g., Group 1 metals, Group 17 halogens).
• Just as a book’s structure helps find information, the periodic table’s organization (periods and groups) helps predict element properties.

Question 12: Halogens (Group 17) properties

• Physical: Non - metals, diatomic molecules (e.g., $\ce{Cl2}$, $\ce{Br2}$), exist as solids (iodine), liquids (bromine), or gases (fluorine, chlorine) at room temperature, colored (e.g., chlorine is yellow - green, bromine is red - brown).
• Chemical: Highly reactive non - metals, gain 1 electron to form $1^-$ ions, react vigorously with metals (e.g., $\ce{2Na + Cl2 -> 2NaCl}$), form salts (halides).

Question 13: Noble Gases (Group 18) properties

• Physical: Colorless, odorless gases at room temperature, very low boiling/melting points (monatomic molecules).
• Chemical: Extremely unreactive (inert) due to a full valence electron shell (8 electrons, except He with 2), rarely form compounds.

Question 14: Sodium (Na) valence electrons

• My Claim: A sodium atom has 1 valence electron.
• My Evidence: Sodium is in Group 1 of the periodic table. For main - group elements, the group number equals the number of valence electrons.

Question 15: Calcium (Ca) energy levels

• My Claim: A calcium atom has 4 energy levels (electron shells).
• My Evidence: Calcium is in Period 4 of the periodic table. The period number (horizontal row) equals the number of occupied energy levels (electron shells) in an atom.

Answer:

s (summarized):

1. Use the element’s group number (main - group: group # = valence e⁻; transition metals: variable).
2. At the top of each vertical column (group).
3. Organized by atomic number (rows = periods, columns = groups) like a book’s pages/sections.
4. Halogens: reactive non - metals, diatomic, form $1^-$ ions, form salts.
5. Noble Gases: inert, monatomic gases, full valence shell.
6. Claim: 1 valence e⁻; Evidence: Group 1.
7. Claim: 4 energy levels; Evidence: Period 4.