Question

How many neutrons are there in \({ }_{35}^{88} \mathrm{Sr}\) ? (a) 38 (b) 50 (c) 126 (d) 88

Short answer

There are 53 neutrons in \( { }_{35}^{88} \mathrm{Sr}\).

Step-by-step solution

Determine the Atomic Number

Identify the atomic number of Strontium (Sr), which is the subscript to the left of the chemical symbol. In this case, it is 35. This number represents the number of protons in the nucleus of an atom of Strontium.

Calculate the Number of Neutrons

Use the atomic mass number (the superscript, which is 88 for Sr) and subtract the atomic number (number of protons, which is 35) to find the number of neutrons: Number of neutrons = Atomic mass number - Atomic number.

Evaluate the Expression

Calculate the number of neutrons using the numbers from Step 2: 88 - 35.

Key concepts

Atomic Number

The atomic number is a fundamental concept in chemistry and is central to understanding the structure of an atom. It is represented by the letter 'Z' and provides an identity to each chemical element. In essence, the atomic number corresponds to the number of protons found in the nucleus of an atom. Since protons are positively charged, the atomic number also indicates the positive charge of the nucleus.

This number is crucial because it not only determines the place of an element in the periodic table but also its chemical properties. For instance, all atoms of the same element have the same atomic number, and thus, the same number of protons. However, they may vary in terms of neutrons and electrons. This characteristic helps us determine the identity of an element during chemical reactions and when assessing isotopes, which are atoms of the same element having different numbers of neutrons.

Atomic Mass Number

The atomic mass number, denoted as 'A', is the total count of protons and neutrons in an atom's nucleus. It's often confused with the atomic weight, the average mass of atoms of an element from a given sample, which can include various isotopes. The key difference is that the atomic mass number is always a whole number since it counts actual subatomic particles, while atomic weight is a weighted average that can be a decimal value.

To clarify, an atom's atomic number (protons) plus the number of its neutrons equals the atomic mass number: \( A = Z + N \), where 'N' is the number of neutrons. This number is vital for understanding isotopes and balancing nuclear reactions, as it indicates the overall 'heaviness' of an atom's nucleus.

Neutron Calculation

Calculating the number of neutrons in an atom is a straightforward process once you have the atomic number and the atomic mass number. The equation for finding the neutron count is: \( N = A - Z \).

This formula tells us that to find the number of neutrons ('N'), you must subtract the atomic number ('Z'), which is the number of protons, from the atomic mass number ('A'). This simple yet critical calculation plays a significant role in understanding the various isotopes of an element and is also essential when studying nuclear physics and conducting chemical analyses.

Chemical Elements

Chemical elements are pure substances consisting of only one type of atom, distinguished by their atomic number. Each element has unique physical and chemical properties and is represented by a symbol on the periodic table. Elements can combine in various ways to form compounds through chemical bonds.

Understanding elements involves more than just their atomic number; we also consider their atomic mass, electron configuration, and isotopes, which can vary in neutron count. These factors contribute to the diversity of chemical behavior among elements, influencing how they interact with one another in chemical reactions and the composition of matter in the universe.