Chapter 4 Part 2: Periodic Table, Ions, and Isotopes

Q17. Can you classify an element based on its location in the periodic table?

Key Terms:

• Metals: left, malleable, conduct electricity

• Non-metals: right, brittle, poor conductors

• Metalloids: staircase

• Main-group elements: Groups 1, 2, and 13–18.

• Transition elements: Groups 3–12.

• Alkali metals: Group 1 (except hydrogen).

• Alkaline earth metals: Group 2.

• Halogens: Group 17.

• Noble gases: Group 18.

Q18. Can you define an ion?

• Ion: An atom or molecule with a net electric charge due to the loss/gain of one or more electrons.

Q19. Can you explain how and why ions form?

Key Terms:

• Cation: A positively charged ion (formed by losing electrons).

• Anion: A negatively charged ion (formed by gaining electrons).

  • When an atom loses electrons, it becomes a cation (positive charge).

  • When an atom gains electrons, it becomes an anion (negative charge).

Q20. Can you explain how ions are different from their neutral atom?

• Neutral atom: Equal numbers of protons and electrons.

• Ion: Unequal numbers of protons and electrons, resulting in a net charge.

Q21. When writing the atomic symbol for an ion, where do you write the charge?

• Atomic symbol: The one- or two-letter abbreviation for an element, sometimes with superscripts and subscripts to indicate charge and mass number/upper right.

Q22. Can you use the periodic table to predict the preferred ion for an element?

• Valence electrons: Electrons in the outermost shell, which determine ion formation.

• Octet rule: Atoms tend to gain or lose electrons to achieve a full outer shell (usually 8 electrons).

1. Identify the group number of the element to determine the number of valence electrons.

2. Apply the octet rule to predict whether the element will gain or lose electrons.

3. Determine the resulting charge based on the number of electrons gained or lost.

Q23. Can you define an isotope?

• Isotope: Atoms of the same element with the same number of protons but different numbers of neutrons.

1. Recall that isotopes have the same atomic number (protons) but different mass numbers (protons + neutrons).

2. Understand that isotopes of an element have nearly identical chemical properties but may have different physical properties.

Q24. Can you explain how and why isotopes form?

• Neutron number: The number of neutrons in the nucleus, which can vary among atoms of the same element.

1. Recall that isotopes form because the number of neutrons in the nucleus can vary while the number of protons remains constant.

2. Understand that natural processes (such as nuclear reactions) can lead to the formation of different isotopes.

Q25. Can you write and interpret atomic symbols for isotopes?

• Atomic symbol for isotopes: $^A_ZX$ where $A$ is the mass number, $Z$ is the atomic number, and $X$ is the element symbol.

1. Identify the element symbol ($X$), atomic number ($Z$), and mass number ($A$).

2. Write the isotope symbol in the correct format: $^A_ZX$.

3. Interpret what each part of the symbol represents.

Q26. Can you write and interpret chemical symbols for isotopes?

• Chemical symbol for isotopes: Element name or symbol followed by mass number (e.g., C-14 or Carbon-14).

1. Write the element symbol or name.

2. Add a hyphen and the mass number (e.g., C-14).

3. Interpret what the mass number indicates about the isotopes

Q27. Can you write and interpret chemical names for isotopes?

• Chemical name for isotopes: Element name followed by mass number (e.g., Carbon-14).

1. Write the full element name.

2. Follow it with a hyphen and the mass number (e.g., Carbon-14).

3. Interpret what the mass number tells you about the isotope.

Q28. Can you define atomic mass?

• Atomic mass: The mass of a single atom, usually expressed in atomic mass units (amu).

1. Recall that atomic mass is the sum of the masses of protons and neutrons in the nucleus.

2. Understand that electrons contribute very little to the total mass.

Q29. Can you define average atomic mass?

• Average atomic mass: The weighted average of the atomic masses of all naturally occurring isotopes of an element.

1. Recall that each isotope has a specific mass and natural abundance.

2. Understand that the average atomic mass is calculated by multiplying each isotope's mass by its fractional abundance and summing the results.

Q30. Can you explain the difference between atomic mass and average atomic mass?

• Atomic mass: Mass of a specific isotope.

• Average atomic mass: Weighted average of all isotopes' masses.

Q31. Can you determine the atomic mass for a neutral element, ion, or isotope?

Key Formula:

$\text{Atomic mass} = \text{Number of protons} + \text{Number of neutrons}$

1. Identify the number of protons (atomic number) and neutrons (mass number - atomic number).

2. Add the number of protons and neutrons to find the atomic mass.

Q32. Can you explain isotope abundance?

• Isotope abundance: The relative amount of each isotope of an element found in nature, usually expressed as a percentage or fraction.

1. Recall that elements can have multiple naturally occurring isotopes.

2. Understand that the abundance of each isotope affects the average atomic mass of the element.

Q33. Can you use isotope abundance and isotope exact masses to calculate the average atomic mass of an element?

Key Formula:

$\text{Average atomic mass} = (\text{fractional abundance}_1 \times \text{mass}_1) + (\text{fractional abundance}_2 \times \text{mass}_2) + \ldots$

1. List the exact mass and fractional abundance for each isotope.

2. Multiply each isotope's mass by its fractional abundance.

3. Add the results to find the average atomic mass.

Q34. Can you determine the number of protons, neutrons, and electrons for a given neutral atom, ion, or isotope?.

Key Steps:

• Protons = atomic number.

• Neutrons = Mass number - atomic number.

• Electrons = protons in a neutral atom; adjust for charge in ions.

1. Identify the atomic number (number of protons).

2. Calculate the number of neutrons (mass number - atomic number).

3. Determine the number of electrons (equal to protons for neutral atoms; adjust for charge in ions).