7. which of the following is true about isotopes?
a) they have different numbers of protons.
b) they have different numbers of electrons.
c) they have different numbers of neutrons.
d) they have the same atomic mass.

8. why are some isotopes radioactive?
a) they have too many protons.
b) they have an unstable ratio of neutrons to protons.
c) they have too many electrons.
d) they have a stable nucleus.

9. which isotope is commonly used in carbon dating?
a) carbon-12
b) carbon-13
c) carbon-14
d) carbon-15

10. what is the primary use of isotopes in medicine?
a) to alter chemical reactions
b) as tracers for diagnosis and treatment
c) to change the color of substances
d) for making medicines

open ended questions: answer the following questions in complete sentences:
1. explain how isotopes of an element can have the same chemical properties despite having different mass numbers.

2. describe the difference between a cation and an anion.

3. how does the formation of ions relate to the stability of an atom?

Question

7. which of the following is true about isotopes?
a) they have different numbers of protons.
b) they have different numbers of electrons.
c) they have different numbers of neutrons.
d) they have the same atomic mass.

8. why are some isotopes radioactive?
a) they have too many protons.
b) they have an unstable ratio of neutrons to protons.
c) they have too many electrons.
d) they have a stable nucleus.

9. which isotope is commonly used in carbon dating?
a) carbon-12
b) carbon-13
c) carbon-14
d) carbon-15

10. what is the primary use of isotopes in medicine?
a) to alter chemical reactions
b) as tracers for diagnosis and treatment
c) to change the color of substances
d) for making medicines

open ended questions: answer the following questions in complete sentences:
1. explain how isotopes of an element can have the same chemical properties despite having different mass numbers.

2. describe the difference between a cation and an anion.

3. how does the formation of ions relate to the stability of an atom?

Accepted Answer

### Question 7
# Brief Explanations:
Isotopes are atoms of the same element with the same number of protons (and electrons, in neutral state) but different numbers of neutrons. So option c is correct as a) is wrong (same protons), b) is wrong (same electrons in neutral), d) is wrong (different atomic mass due to different neutrons).
# Answer:
c) They have different numbers of neutrons.

### Question 8
# Brief Explanations:
Radioactive isotopes (radioisotopes) are unstable because their neutron - proton ratio is unstable. Too many protons (A) or electrons (C) don't cause radioactivity. A stable nucleus (D) would not be radioactive. So B is correct.
# Answer:
B) They have an unstable ratio of neutrons to protons.

### Question 9
# Brief Explanations:
Carbon - 14 is the isotope commonly used in carbon dating. Carbon - 12 is stable and the main carbon isotope, Carbon - 13 is also stable, and Carbon - 15 is not used for carbon dating.
# Answer:
C) Carbon - 14

### Question 10
# Brief Explanations:
In medicine, isotopes are mainly used as tracers for diagnosis (like in imaging) and treatment (like in radiation therapy). They don't alter chemical reactions (A), change color (C), or are mainly for making medicines (D). So B is correct.
# Answer:
B) As tracers for diagnosis and treatment

### Open Ended Question 1
# Brief Explanations:
Chemical properties of an atom are determined by the number of electrons in its outermost shell (valence electrons), which is determined by the number of protons (atomic number). Isotopes of an element have the same number of protons, so they have the same electron configuration (in neutral state), especially the same number of valence electrons. Since valence electrons are responsible for chemical bonding and reactions, isotopes with different mass numbers (due to different neutrons) have the same chemical properties.
# Answer:
Isotopes of an element have the same number of protons, so they have the same electron configuration (including the same number of valence electrons). Chemical properties are determined by valence electrons (which govern bonding and reactions), so despite different mass numbers (from different neutrons), isotopes have the same chemical properties.

### Open Ended Question 2
# Brief Explanations:
A cation is a positively charged ion formed when an atom loses one or more electrons (usually to achieve a stable electron configuration, like a noble gas configuration). An anion is a negatively charged ion formed when an atom gains one or more electrons (also to achieve a stable electron configuration). The key difference is their charge (cation: positive, anion: negative) and the process of formation (cation: electron loss, anion: electron gain).
# Answer:
A cation is a positively charged ion formed by an atom losing one or more electrons (e.g., $\ce{Na^+}$ from $\ce{Na}$ losing an electron). An anion is a negatively charged ion formed by an atom gaining one or more electrons (e.g., $\ce{Cl^-}$ from $\ce{Cl}$ gaining an electron). Cations have a positive charge, anions have a negative charge; cations form via electron loss, anions via electron gain.

### Open Ended Question 3
# Brief Explanations:
Atoms are stable when their outermost electron shell is full (or has a stable configuration, like noble gases with 8 valence electrons, or 2 for hydrogen/helium). Atoms that don't have a stable electron configuration (e.g., atoms with 1, 2, or 7 valence electrons) can form ions by gaining or losing electrons. For example, a sodium atom ($\ce{Na}$) has 1 valence electron, which is unstable. It loses that electron to form $\ce{Na^+}$, which has a stable electron configuration (like neon). A chlorine atom ($\ce{Cl}$) has 7 valence electrons, so it gains an electron to form $\ce{Cl^-}$, with a stable configuration (like argon). So the formation of ions is a way for atoms to achieve a stable electron configuration, thus increasing their stability.
# Answer:
Atoms are stable when their outermost electron shell has a stable configuration (e.g., 8 valence electrons, or 2 for $\ce{H/He}$). Atoms with unstable electron configurations (e.g., incomplete valence shells) form ions by gaining or losing electrons to achieve a stable configuration (like noble gases). For example, $\ce{Na}$ (1 valence electron) loses an electron to form $\ce{Na^+}$ (stable, like $\ce{Ne}$), and $\ce{Cl}$ (7 valence electrons) gains an electron to form $\ce{Cl^-}$ (stable, like $\ce{Ar}$). Thus, ion formation helps atoms achieve stability.

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