Question

comprehension questions on atoms and elements

1. describe how the atomic number of an element is determined and what it signifies. (timestamp: 0:41)
2. in the periodic table, how can you find the mass number of an element? what does it consist of? (timestamp: 1:18)
3. explain the difference between ions and isotopes based on the information provided in the video. (timestamp: 1:51, 2:57)
4. what happens to the number of electrons when an atom becomes a positive ion? provide an example. (timestamp: 2:45)
5. identify and differentiate between the three isotopes of hydrogen mentioned in the video. (timestamp: 3:12)

Explanation:

Step1: Define atomic number

The atomic number of an element is determined by the number of protons in the nucleus of an atom of that element. It signifies the element's identity and its position in the periodic table. For example, hydrogen has 1 proton, so its atomic number is 1.

Step2: Find mass number in periodic table

In the periodic table, the mass number of an element is usually given as the average atomic mass (a weighted - average of the masses of its isotopes). The mass number consists of the sum of protons and neutrons in the nucleus of an atom. For example, carbon - 12 has 6 protons and 6 neutrons, so its mass number is 12.

Step3: Differentiate ions and isotopes

Ions are atoms or molecules that have gained or lost electrons, resulting in a net electrical charge. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. For example, $\text{Na}^+$ is a sodium ion (lost 1 electron), and carbon - 12 and carbon - 14 are isotopes of carbon.

Step4: Analyze electron change in positive ion

When an atom becomes a positive ion, it loses electrons. For example, a sodium atom (Na) has 11 electrons. When it becomes a sodium ion ($\text{Na}^+$), it loses 1 electron and has 10 electrons.

Step5: Identify hydrogen isotopes

The three isotopes of hydrogen are protium (1 proton, 0 neutrons), deuterium (1 proton, 1 neutron), and tritium (1 proton, 2 neutrons). Protium is the most common isotope. Deuterium is also called heavy hydrogen, and tritium is radioactive.

Answer:

1. The atomic number is determined by the number of protons in the nucleus. It signifies the element's identity and position in the periodic table.
2. The mass number is usually the average atomic mass in the periodic table. It consists of the sum of protons and neutrons.
3. Ions are atoms/molecules with a net charge due to electron gain/loss. Isotopes are atoms of the same element with different neutron numbers.
4. The atom loses electrons. For example, Na loses 1 electron to become $\text{Na}^+$.
5. Protium: 1 proton, 0 neutrons; Deuterium: 1 proton, 1 neutron; Tritium: 1 proton, 2 neutrons.