Question

If the number of protons in a neutral atom is 92 and its mass number is 238 : a. What is the name of that element? b. How many electrons does it have? c. How many neutrons does it have?

Short answer

a. Uranium b. 92 electrons c. 146 neutrons

Step-by-step solution

Identifying the Element

To identify the element, we need to know its atomic number. The atomic number is equivalent to the number of protons in a neutral atom. Since the number of protons is 92, we look at the periodic table and find that the element with atomic number 92 is Uranium.

Determining the Number of Electrons

In a neutral atom, the number of protons is equal to the number of electrons. Since the atom has 92 protons, it also has 92 electrons.

Calculating the Number of Neutrons

The number of neutrons can be found by subtracting the atomic number from the mass number. The mass number is the sum of protons and neutrons. Hence, the number of neutrons is given by: \( 238 - 92 = 146 \). Therefore, this atom contains 146 neutrons.

Key concepts

Protons and Neutrons

Protons and neutrons are fundamental components of an atom's nucleus. Protons carry a positive charge, while neutrons are neutral. This means they have no charge. The number of protons in an atom is pivotal because it defines what element the atom is. For example, if an atom has 92 protons, it is Uranium, as per the periodic table. The atomic number represents the number of protons. Therefore, protons are essential for identifying an element.
Neutrons, on the other hand, are massively essential for the stability of the nucleus, but they don't define the element. The number of neutrons in an atom can vary even within the same element. When they do vary, they form isotopes. The sum of protons and neutrons gives us the mass number of the atom. For example, if Uranium has a mass number of 238, we can calculate the number of neutrons by subtracting the atomic number (92 for Uranium) from the mass number (238). This gives us 146 neutrons.

Periodic Table

The periodic table is an organized arrangement of all known chemical elements. It is crucial for locating and identifying elements based on their atomic number, electron configuration, and chemical properties. The table is arranged in rows called periods and columns known as groups. Elements are listed in order of increasing atomic number, starting with Hydrogen.

• Atomic Number: This number tells us the number of protons in the nucleus of an atom. It determines which element it is. For example, Uranium has an atomic number of 92.
• Groups and Periods: These help scientists infer an element’s chemical properties. Elements in the same group tend to have similar chemical characteristics.
• Element Symbol: Each element is assigned a one or two-letter abbreviation known as a symbol.

The periodic table is a vital tool for scientists and students alike for understanding how different elements relate to one another.

Neutral Atom

A neutral atom is an atom where the number of electrons is equal to the number of protons. This balance means that the positive charge of the protons is perfectly canceled out by the negative charge of the electrons. As a result, the atom as a whole holds no overall charge. For instance, take the atom with 92 protons we mentioned earlier. In a neutral state, this Uranium atom also has 92 electrons. These electrons orbit the nucleus and are crucial for chemical bonds and interactions between elements. When talking about ions, they arise when an atom loses or gains electrons resulting in a charge imbalance. Understanding what makes up a neutral atom helps us grasp more complex concepts such as ionization and reactivity, providing a solid grounding for further chemistry studies.