5. how does a neutral atom become positive or negative?
*hint: how does an atom obtain a charge?

6. what is the difference between physical property and a chemical property of an atom or compound?

7. what are 3 out of 5 chemical changes?

8. why are radicals (polyatomic ions) not considered to be compounds?

9. what type of bond is found in a polyatomic ion (radical) when all of the atoms are nonmetals?

10. of all the metals found on the periodic table of elements under what group are the most active metals?
11. draw a diagram of the lewis model for the compound mgcl₂.

12. fill out the following chart:

| element | proton | neutron | electron |
| ---- | ---- | ---- | ---- |
| magnesium | | | |
| aluminum | | | |
| chlorine | | | |
13. what is the difference between boron - 9 and boron - 11? *hint: think what is changing and what is the term?

Question

5. how does a neutral atom become positive or negative?
*hint: how does an atom obtain a charge?

6. what is the difference between physical property and a chemical property of an atom or compound?

7. what are 3 out of 5 chemical changes?

8. why are radicals (polyatomic ions) not considered to be compounds?

9. what type of bond is found in a polyatomic ion (radical) when all of the atoms are nonmetals?

10. of all the metals found on the periodic table of elements under what group are the most active metals?
11. draw a diagram of the lewis model for the compound mgcl₂.

12. fill out the following chart:

| element | proton | neutron | electron |
| ---- | ---- | ---- | ---- |
| magnesium |  |  |  |
| aluminum |  |  |  |
| chlorine |  |  |  |
13. what is the difference between boron - 9 and boron - 11? *hint: think what is changing and what is the term?

Accepted Answer

### Question 5
# Brief Explanations:
A neutral atom becomes positive or negative (forms an ion) by gaining or losing electrons. Atoms have equal numbers of protons (positive charge) and electrons (negative charge) in the neutral state. If an atom loses electrons, it has more protons than electrons, so it becomes a positive ion (cation). If it gains electrons, it has more electrons than protons, so it becomes a negative ion (anion).
# Answer:
A neutral atom becomes positive (cation) by losing electrons and negative (anion) by gaining electrons.

### Question 6
# Brief Explanations:
A physical property of an atom or compound is a characteristic that can be observed or measured without changing the substance's chemical identity (e.g., color, density, melting point). A chemical property describes how a substance reacts with other substances to form new substances (e.g., flammability, reactivity with acids, ability to rust).
# Answer:
Physical property: observable/measurable without chemical change (e.g., color, density). Chemical property: describes chemical reactivity (e.g., flammability, reactivity with acids).

### Question 7
# Brief Explanations:
Five common chemical changes include combustion (burning), rusting (oxidation of iron), decomposition (e.g., breaking down of hydrogen peroxide), acid - base neutralization (e.g., reaction of HCl and NaOH), and fermentation (e.g., yeast converting sugar to alcohol). Three of these are combustion, rusting, and decomposition.
# Answer:
Three chemical changes: Combustion (e.g., burning wood), Rusting (e.g., iron rusting), Decomposition (e.g., $H_2O_2$ breaking down).

### Question 8
# Brief Explanations:
A compound is a substance made of two or more different elements chemically combined in a fixed ratio and is neutral (has no net charge). Radicals (polyatomic ions) have a net positive or negative charge (they are ions) and do not have a neutral charge, so they do not meet the definition of a compound. Also, compounds are made of neutral molecules or formula units in a neutral state, while polyatomic ions are charged species.
# Answer:
Radicals (polyatomic ions) are charged (have net charge), but compounds are neutral and consist of elements in fixed ratios without a net charge.

### Question 9
# Brief Explanations:
When all atoms in a polyatomic ion (radical) are nonmetals, the bond between them is a covalent bond. Nonmetals share electrons to achieve stable electron configurations, and in polyatomic ions, the atoms are held together by covalent bonds (even though the ion as a whole is charged). For example, in the sulfate ion ($SO_4^{2 - }$), the S and O atoms are bonded covalently.
# Answer:
The type of bond in a polyatomic ion with all nonmetal atoms is a covalent bond.

### Question 10
# Brief Explanations:
On the Periodic Table, the most active metals are in Group 1 (the alkali metals, e.g., lithium, sodium, potassium). These metals have one valence electron, which they readily lose to form positive ions, making them very reactive.
# Answer:
The most active metals are in Group 1 (Alkali Metals) of the Periodic Table.

### Question 11
# Explanation:
## Step 1: Determine the valence electrons
Magnesium (Mg) is in Group 2, so it has 2 valence electrons. Chlorine (Cl) is in Group 17, so it has 7 valence electrons.
## Step 2: Ionic bond formation
Mg will lose its 2 valence electrons to achieve a stable octet (like Ne). Each Cl atom needs 1 electron to achieve a stable octet (like Ar). So one Mg atom will transfer its 2 electrons to two Cl atoms.
## Step 3: Draw the Lewis structure
- Mg: Write the symbol Mg. Represent its 2 valence electrons as dots (or just show that it loses them).
- Cl: For each Cl, write the symbol Cl with 7 valence electrons (3 pairs and 1 unpaired). After Mg loses 2 electrons, each Cl gains 1 electron. So we have $[Cl^ - ]$ with 8 valence electrons (4 pairs) around each Cl, and $Mg^{2 + }$ with no valence electrons (since it lost them). The Lewis structure for $MgCl_2$ is $[:\ddot{Cl}:]^ - Mg^{2 + }[:\ddot{Cl}:]^ - $
# Answer:
The Lewis Model for $MgCl_2$ shows $Mg^{2 + }$ (with no valence electrons shown as it lost 2 electrons) and two $[:\ddot{Cl}:]^ - $ (each with 8 valence electrons, 4 pairs) with the $Mg^{2 + }$ in the middle between the two $Cl^ - $ ions.

### Question 12
# Explanation:
## Step 1: Magnesium
- Atomic number of Mg is 12. Protons = atomic number = 12.
- Mass number of Mg is approximately 24. Neutrons = mass number - protons = 24 - 12 = 12.
- In a neutral atom, electrons = protons = 12.
## Step 2: Aluminum
- Atomic number of Al is 13. Protons = 13.
- Mass number of Al is approximately 27. Neutrons = 27 - 13 = 14.
- Electrons = protons = 13 (neutral atom).
## Step 3: Chlorine
- Atomic number of Cl is 17. Protons = 17.
- Mass number of Cl is approximately 35. Neutrons = 35 - 17 = 18.
- Electrons = protons = 17 (neutral atom).
# Answer:
| Element   | Proton | Neutron | Electron |
|-----------|--------|---------|----------|
| magnesium | 12     | 12      | 12       |
| aluminum  | 13     | 14      | 13       |
| chlorine  | 17     | 18      | 17       |

### Question 13
# Brief Explanations:
Boron - 9 and Boron - 11 are isotopes of Boron. Isotopes are atoms of the same element with the same number of protons (atomic number) but different numbers of neutrons (and thus different mass numbers). Boron has an atomic number of 5 (so 5 protons). For Boron - 9: mass number = 9, neutrons = 9 - 5 = 4. For Boron - 11: mass number = 11, neutrons = 11 - 5 = 6. The difference is in the number of neutrons (they are isotopes).
# Answer:
Boron - 9 and Boron - 11 are isotopes. They have the same number of protons (5) but different numbers of neutrons (B - 9 has 4 neutrons, B - 11 has 6 neutrons).

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