This worksheet explores the fundamental concepts of atoms, isotopes, and ions. Understanding these building blocks of matter is crucial for grasping more complex chemical concepts. This guide will provide a clear explanation of each term, followed by practice exercises to solidify your understanding.
What are Atoms?
Atoms are the basic units of matter. They are incredibly small and consist of three primary subatomic particles:
- Protons: Positively charged particles found in the atom's nucleus. The number of protons defines the element (atomic number).
- Neutrons: Neutrally charged particles also located in the nucleus. The number of neutrons can vary within an element, leading to isotopes (discussed below).
- Electrons: Negatively charged particles that orbit the nucleus in electron shells or energy levels. The number of electrons typically equals the number of protons in a neutral atom.
Atoms are electrically neutral when the number of protons equals the number of electrons. The mass of an atom is primarily determined by the number of protons and neutrons, as electrons have negligible mass.
What are Isotopes?
Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons. This variation in neutron number leads to different mass numbers (protons + neutrons). While isotopes of an element have similar chemical properties, their physical properties, like mass, can differ.
Example: Carbon-12 (¹²C) and Carbon-14 (¹⁴C) are isotopes of carbon. Both have 6 protons, but ¹²C has 6 neutrons, while ¹⁴C has 8 neutrons. ¹⁴C is radioactive, a key difference from the stable ¹²C.
What are Ions?
Ions are atoms or molecules that have gained or lost electrons, resulting in a net electrical charge.
- Cations: Positively charged ions formed when an atom loses electrons. Metals tend to form cations.
- Anions: Negatively charged ions formed when an atom gains electrons. Nonmetals tend to form anions.
Example: A sodium atom (Na) loses one electron to become a sodium ion (Na⁺), a cation. A chlorine atom (Cl) gains one electron to become a chloride ion (Cl⁻), an anion.
Practice Exercises: Atoms, Isotopes, and Ions
Part 1: Identifying Subatomic Particles
- An atom of oxygen (O) has 8 protons. How many electrons does a neutral oxygen atom have?
- An atom of aluminum (Al) has 13 protons and 14 neutrons. What is its mass number?
- An ion of magnesium (Mg) has 12 protons and 10 electrons. What is its charge?
Part 2: Isotope Identification
- Two isotopes of potassium (K) are ³⁹K and ⁴¹K. How many protons, neutrons, and electrons are present in each isotope (assuming neutral atoms)?
- Explain why isotopes of the same element have similar chemical properties but can have different physical properties.
Part 3: Ion Identification
- A sulfur atom (S) gains two electrons. What is the resulting ion and its charge?
- A calcium atom (Ca) loses two electrons. What is the resulting ion and its charge?
Part 4: Challenge Question
An element has two isotopes, one with a mass number of 63 and the other with a mass number of 65. The average atomic mass of the element is 63.55 amu. What is the relative abundance of each isotope? (Hint: Use a weighted average calculation)
This worksheet provides a foundational understanding of atoms, isotopes, and ions. Further exploration into the periodic table and chemical bonding will build upon these core concepts. Remember to consult your textbook or other learning resources for additional support and practice problems.
