Problem 120 - Introductory Chemistry Atoms First

Question

Complete the following statements: (a) The nucleus contains the charged particles in the atom. (b) The particles in the nucleus are the and (c) Almost all of the mass of an atom is contained in the (d) The two particles whose charges cancel to make an atom neutral are and

Step-by-Step Solution

Answer

(a) The nucleus contains the positively charged particles and the chargeless particles in the atom. (b) The particles in the nucleus are the protons and neutrons. (c) Almost all of the mass of an atom is contained in the nucleus. (d) The two particles whose charges cancel to make an atom neutral are protons and electrons.

Step 1: Identify the fundamental particles in an atom

An atom is composed of three fundamental particles: protons, neutrons, and electrons. Protons are positively charged, neutrons are neutral (no charge), and electrons are negatively charged.

Step 2: Complete statement (a)

We know that the nucleus contains the charged particles in the atom, which are protons (positively charged) and neutrons (chargeless). (a) The nucleus contains the positively charged particles and the chargeless particles in the atom.

Step 3: Complete statement (b)

Since the nucleus contains protons and neutrons, we can complete the statement as follows: (b) The particles in the nucleus are the protons and neutrons.

Step 4: Complete statement (c)

The nucleus contains protons and neutrons, which have much more mass than electrons. Therefore, (c) can be completed as: (c) Almost all of the mass of an atom is contained in the nucleus.

Step 5: Complete statement (d)

To make an atom neutral, the charges of the fundamental particles must cancel out. This occurs when the number of positively charged protons is equal to the number of negatively charged electrons. The charges of protons and electrons cancel out each other when there are an equal number of both. (d) The two particles whose charges cancel to make an atom neutral are protons and electrons.

Key Concepts

Nucleus

At the heart of every atom is the nucleus. It is a dense region located at the center, comprised predominantly of two types of subatomic particles: protons and neutrons. Despite its small size, the nucleus houses almost all of the atom's mass. This is because both protons and neutrons have relatively significant mass compared to electrons. However, unlike electrons, neutrons possess no charge.

• The nucleus is responsible for almost the entirety of an atom's mass.
• It is tightly packed with protons and neutrons.
• Both protons and neutrons are much heavier than electrons.

The binding energy that holds the nucleus together is crucial, as it determines the stability of the atom. Without the nucleus, there would be no atomic structure to speak of.

Protons

Protons are subatomic particles found within the nucleus of an atom. They carry a positive electrical charge, denoted as "+1". The number of protons in an atom's nucleus is known as the atomic number, a unique identifier for chemical elements. For example, hydrogen atoms have one proton, while helium atoms have two.

• Protons determine the identity of an element.
• They contribute significantly to the mass of the nucleus.
• The positive charge of protons helps balance out the negative charge of electrons.

This balance between protons and electrons is essential for the atom to maintain a neutral charge overall. The presence of protons in the nucleus also influences how atoms interact with each other, dictating chemical properties.

Neutrons

Neutrons are neutrally charged particles located in the nucleus alongside protons. These particles have no electrical charge, which is why they are termed 'neutral.' Despite the lack of charge, neutrons play a crucial role in the stability of the nucleus.

• Neutrons contribute to the atomic mass without affecting the charge.
• They help stabilize the nucleus by separating protons and reducing repulsive forces.
• The number of neutrons can vary in the same element resulting in isotopes.

The presence of neutrons helps in offsetting the electrostatic repulsion between positively charged protons. This ensures that the nucleus remains intact. Variations in neutron number can lead to the formation of isotopes, which can have different physical properties.

Electrons

Electrons are lightweight, negatively charged particles that orbit the nucleus of an atom. They are much smaller than both protons and neutrons, contributing negligibly to the atom's overall mass. Despite their small size, electrons play a vital role in atomic structure.

• Electrons are negatively charged, indicated by "-1".
• They exist in an electron cloud around the nucleus.
• The number of electrons equals the number of protons, ensuring the atom is neutral.

Electrons are involved in forming chemical bonds and reactions, as they can be shared, gained, or lost in processes that result in the creation of molecules. The interaction of electrons between atoms dictates how substances combine and react with one another, forming the basis of chemistry.