elements & compounds unit review
group a: periodic table & bonding
as a group, look at your periodic table. discuss the patterns we noticed on the table.
1. what pattern do we notice within each column?

2. what pattern do we notice within each row?

3. what pattern repeats every time a new row begins?

4. which column of elements never reacts with other elements, and why?

5. why is it so likely that elements from columns 1 and 7 will react?

6. what other 2 columns would be really likely to react?

Question

elements & compounds unit review
group a: periodic table & bonding
as a group, look at your periodic table. discuss the patterns we noticed on the table.
1. what pattern do we notice within each column?

2. what pattern do we notice within each row?

3. what pattern repeats every time a new row begins?

4. which column of elements never reacts with other elements, and why?

5. why is it so likely that elements from columns 1 and 7 will react?

6. what other 2 columns would be really likely to react?

Accepted Answer

### Question 1
# Brief Explanations:
Within each column (group) of the periodic table, elements have similar chemical properties. This is because they have the same number of valence electrons. For example, all elements in Group 1 (alkali metals) have 1 valence electron, which makes them highly reactive and likely to lose that electron in chemical reactions. Similarly, Group 17 (halogens) have 7 valence electrons and tend to gain 1 electron. The number of electron shells may increase down the group, but the valence electron configuration (which determines chemical behavior) remains the same.
# Answer:
Elements in each column (group) have similar chemical properties because they have the same number of valence electrons. The number of electron shells increases down the column, but valence electron count (and thus chemical reactivity patterns) stays consistent.

### Question 2
# Brief Explanations:
Within each row (period) of the periodic table, elements show a pattern of increasing atomic number (number of protons/electrons). As you move from left to right across a period, the number of valence electrons increases from 1 to 8 (or 2 for the first period). This leads to a change in chemical properties: elements start as metals on the left, transition to metalloids, and then to non - metals on the right. Also, atomic radius generally decreases from left to right across a period because the increasing positive charge of the nucleus pulls the electrons in the same energy level closer.
# Answer:
As you move across a row (period) from left to right, atomic number (protons/electrons) increases, valence electrons increase from 1 - 8 (or 2), elements change from metals to non - metals, and atomic radius generally decreases. Chemical properties change from metallic (left) to non - metallic (right) behavior.

### Question 3
# Brief Explanations:
When a new row (period) begins in the periodic table, the pattern of electron shell filling and chemical properties repeats. The first element of each new row is an alkali metal (Group 1) with 1 valence electron in a new electron shell. Then, as you move across the period, the number of valence electrons increases, and the chemical properties transition from metallic to non - metallic, similar to the previous period. This is the periodic law in action, where chemical and physical properties of elements are periodic functions of their atomic numbers.
# Answer:
When a new row (period) begins, the pattern of electron shell filling and chemical property trends (from metallic to non - metallic, with increasing valence electrons) repeats. The first element of each new row is an alkali metal (Group 1) with 1 valence electron in a new shell, and the overall trend of property change across the period mirrors that of the previous period.

### Question 4
# Brief Explanations:
The column (group) of elements that never reacts with other elements (or reacts very rarely) is Group 18, the noble gases. Noble gases have a full valence electron shell (2 electrons for helium, 8 electrons for neon, argon, etc.). A full valence shell means that these elements have a stable electron configuration. Since chemical reactions involve the gain, loss, or sharing of electrons to achieve a stable electron configuration, noble gases, having already achieved stability, have no tendency to react with other elements to gain, lose, or share electrons.
# Answer:
The column (Group 18) of noble gases never (or rarely) reacts with other elements. This is because they have a full valence electron shell, giving them a stable electron configuration, so they have no need to gain, lose, or share electrons to achieve stability.

### Question 5
# Brief Explanations:
Elements from column 1 (Group 1, alkali metals) have 1 valence electron. They are highly reactive and tend to lose this single valence electron to achieve a stable electron configuration (like a noble gas). Elements from column 7 (Group 17, halogens) have 7 valence electrons and tend to gain 1 electron to achieve a stable octet (8 valence electrons). So, alkali metals (Group 1) can easily lose their 1 valence electron, and halogens (Group 17) can easily gain that electron. This electron transfer (or sharing in some cases) leads to the formation of ionic (or covalent) compounds, making a reaction between them very likely.
# Answer:
Elements from column 1 (Group 1, alkali metals) have 1 valence electron (tend to lose it), and elements from column 7 (Group 17, halogens) have 7 valence electrons (tend to gain 1). The alkali metal can easily lose its 1 valence electron, and the halogen can easily gain it to achieve stable electron configurations, so they are very likely to react (often forming ionic compounds).

### Question 6
# Brief Explanations:
Two other columns (groups) that are really likely to react are Group 2 (alkaline earth metals) and Group 16 (chalcogens). Group 2 elements have 2 valence electrons and tend to lose them to achieve a stable electron configuration. Group 16 elements have 6 valence electrons and tend to gain 2 electrons. So, Group 2 elements can lose 2 electrons, and Group 16 elements can gain 2 electrons, leading to a favorable electron transfer for chemical bonding (usually ionic bonding). Another pair could be Group 2 and Group 17 (halogens), as Group 2 can lose 2 electrons and Group 17 can gain 1 electron (so two Group 17 elements can react with one Group 2 element).
# Answer:
Two columns that are likely to react are Group 2 (alkaline earth metals) and Group 16 (chalcogens) (since Group 2 loses 2 electrons, Group 16 gains 2) or Group 2 and Group 17 (Group 2 loses 2, Group 17 gains 1, so a 1:2 reaction ratio is possible).

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