Problem 6 - Campbell Biology

Question

We can represent atoms by listing the number of protons, neutrons, and electrons - for example, \(2 p ^ { + } , 2 n ^ { 0 } , 2 e ^ { \circ }\) for helium. Which of the following represents the "O isotope of oxygen? (A) \(7 p ^ { + } , 2 n ^ { 0 } , 9 e ^ { - }\) (B) \(8 p ^ { + } , 10 n ^ { 0 } , 8 e ^ { - }\) (C) \(9 p ^ { + } , 9 n ^ { 0 } , 9 e ^ { - }\) (D) \(10 p ^ { + } , 8 n ^ { 0 } , 9 e ^ { - }\)

Step-by-Step Solution

Answer

(B) 8 protons, 10 neutrons, 8 electrons

Step 1 - Understand the concept of isotopes

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.

Step 2 - Identify the number of protons in oxygen

Oxygen is an element with an atomic number of 8, which means it has 8 protons. Therefore, any isotope of oxygen will have 8 protons.

Step 3 - Examine the given options

Review each option to select the one with 8 protons: (A) 7 protons (B) 8 protons (C) 9 protons (D) 10 protons

Step 4 - Select the correct option

Only option (B) has 8 protons. Therefore, (B) represents an isotope of oxygen.

Step 5 - Verify the neutron count

An isotope has a variable number of neutrons. Option (B) has 10 neutrons, which is a valid count for an isotope.

Step 6 - Verify the electron count

Option (B) has 8 electrons, indicating a neutral atom since the number of protons equals the number of electrons.

Key Concepts

Atomic Structure

Atomic structure is the arrangement of subatomic particles within an atom. These particles include protons, neutrons, and electrons. The combination of these particles determines the identity and properties of the element. The nucleus of an atom consists of protons and neutrons, while electrons orbit around this nucleus in energy levels or shells. Understanding atomic structure helps us to predict the behavior and interaction of atoms.

An atom is mostly empty space, with electrons darting around the dense nucleus at various distances. The structure is important because it defines how elements will react, bond, or form compounds. Each element has a unique atomic structure which is reflected in its atomic number – the number of protons found in the nucleus.

Protons

Protons are positively charged subatomic particles found in the nucleus of an atom. The number of protons in the nucleus is called the atomic number, and it uniquely identifies an element. For example, oxygen has an atomic number of 8, meaning every oxygen atom has 8 protons.

Protons hold a charge of +1 and have a relative mass of about 1 atomic mass unit (amu). They play a key role in binding the nucleus together with neutrons and in determining the element's identity. The number of protons also influences how the atom interacts with electrons to form chemical bonds and stabilize the atom.

Neutrons

Neutrons are neutral subatomic particles, meaning they have no charge. They are found in the nucleus alongside protons. Neutrons stabilize the nucleus, especially as the number of protons increases, by adding mass and spacing out the positively charged protons to reduce repulsive forces.

The number of neutrons can vary in atoms of the same element, creating isotopes. Isotopes are variants of an element that have the same number of protons but different numbers of neutrons. For example, an oxygen isotope can have 8 or 10 neutrons, leading to different isotopes like Oxygen-16 and Oxygen-18. Mass number, which is the sum of protons and neutrons, differs in isotopes due to the neutron count.

Electrons

Electrons are subatomic particles with a negative charge and very little mass, approximately 1/1836 of a proton's mass. They orbit the nucleus in different energy levels or shells, creating a cloud of negative charge around the atom. The arrangement of electrons determines how an atom will react chemically.

In a neutral atom, the number of electrons equals the number of protons. Electrons play a central role in chemical reactions, as they are involved in forming bonds between atoms. When atoms gain or lose electrons, they become ions, which have net charges. Electrons are key to understanding electricity, bonding, and the physical properties of elements.