Question

Consider an atom of 10 \(\mathrm{B}\) . (a) How many protons, neutrons, and electrons does this atom contain? (b) What is the symbol of the atom obtained by adding one proton to \(^{10} \mathrm{B} ?\) (c) What is the symbol of the atom obtained by adding one neutron to 10 \(\mathrm{B}\) ? (c) What is the symbol of the atom obtained by adding one neutron to 10 \(\mathrm{B} ?(\mathbf{d})\) Are either of the atoms obtained in parts (b) and (c) isotopes of 10 \(\mathrm{B} ?\) If so which one?

Short answer

The 10B atom contains 5 protons, 5 neutrons, and 5 electrons. Adding a proton to 10B results in the symbol 10C, while adding a neutron results in the symbol 11B. Among these, only the atom 11B is an isotope of 10B, as it has the same atomic number but with a different mass number.

Step-by-step solution

Identifying the number of protons, neutrons, and electrons in 10B

The isotope notation 10B indicates that this atom has 5 protons (since the atomic number of Boron, B, is 5) and 5 neutrons (as the mass number is 10, i.e., 10 = 5 (protons) + 5 (neutrons)). Since the atom is neutral, it contains 5 electrons, which is equal to the number of protons.

Adding a proton to 10B

To obtain the symbol for the atom formed by adding a proton to 10B, we need to increase its atomic number by 1. So, the new atomic number will be 5+1=6, which corresponds to the element Carbon (C). The new mass number will be the same, so the symbol for the new atom is 10C.

Adding a neutron to 10B

To obtain the symbol for the atom formed by adding a neutron to 10B, we need to increase the mass number by 1 but keep the atomic number constant. So, the new mass number will be 10+1=11, and the new symbol for the atom is 11B.

EndNote: Isotopes determination

For an atom to be an isotope of another, it must have the same atomic number but different mass numbers. Looking at the atoms defined in Step 2 and Step 3, we can see that adding a neutron created an isotope of 10B (11B) since the atomic number remained the same but the mass number changed. Adding a proton did not create an isotope of 10B because the atomic number changed, resulting in a different element (Carbon).

Key concepts

Atomic Number

The atomic number of an element is a fundamental characteristic that defines the identity of the atom. It tells us the number of protons present in the nucleus of the atom. Since protons are positively charged, the atomic number also indicates the charge of the nucleus. For example, the atomic number of boron (B) is 5, which means that any atom of boron will always have 5 protons in its nucleus.

Understanding the atomic number is crucial because it also determines the chemical properties of the atom. In a neutral atom, the number of protons (which are positive) is balanced by an equal number of electrons (which are negative), so the atomic number also tells us how many electrons are in a neutral atom. This balance between protons and electrons gives the atom its chemical identity and is crucial for predicting how it will react with other atoms.

Significance in the Periodic Table

Elements in the periodic table are arranged in order of increasing atomic number. This arrangement shows patterns in elemental properties and helps predict how elements will behave. For instance, elements with similar atomic numbers often have similar chemical properties because they have similar electron configurations.

Mass Number

The mass number is the sum of the number of protons plus the number of neutrons in an atom's nucleus. Unlike the atomic number, the mass number is not unique to a particular element. This is because an element can have atoms with different numbers of neutrons, known as isotopes. The mass number is important because it reflects the isotope of the element.

For instance, in the given problem about boron (B), the isotope is specified with a mass number of 10. Here, the mass number helps us determine that there are 5 neutrons present, since boron's atomic number is 5 (indicating 5 protons), and subtracting the 5 protons from the mass number (10) leaves us with 5 neutrons.

Isotope Variations

Mass numbers vary between isotopes of the same element because each isotope has a different number of neutrons. This difference doesn't affect the chemical properties significantly but does influence the atomic mass and can have large effects in nuclear reactions.

Neutrons in Isotopes

Isotopes are variations of elements that have the same number of protons but a different number of neutrons. While the atomic number remains constant within a particular element's isotopes, the mass number varies due to the change in the number of neutrons.

Using the example of boron from the textbook problem, we can see that by adding a neutron to the original 10B, we increase its mass number by one, resulting in a new isotope 11B. Importantly, because the atomic number remains unchanged (still 5), 11B is still an isotope of boron. This illustrates a common way isotopes are formed – by the addition or loss of neutrons.

Stable versus Radioactive Isotopes

Some isotopes are stable, while others are radioactive and decay over time. This is due to the delicate balance of forces within the nucleus; too many or too few neutrons can make the atom unstable. Radioactive isotopes have many applications, including in medical imaging and treatments, as well as dating ancient materials.

Protons and Electrons in Atoms

Atoms are made up of three primary particles: protons, neutrons, and electrons. Protons and electrons carry charges, positive and negative, respectively. In a neutral atom, the number of protons equals the number of electrons, ensuring that the overall charge is zero.

In an atomic symbol like 10B, we use the atomic number to identify the number of protons, which determines the element identity, and, since the atom is neutral, it's also the number of electrons. In our example, boron has 5 protons and consequently 5 electrons. When an atom gains or loses electrons, it becomes an ion, which has an electrical charge due to the imbalance between protons and electrons.

Protons: The Identity Marker

Protons are the defining feature of an element's identity. Changing the number of protons, as seen when adding a proton to 10B to create a 10C atom, changes the element itself. This is a key point in understanding how elements transform in nuclear reactions and why isotopes remain the same element—they retain the same number of protons.