Atomic Number & Mass Number | Properties of Matter | Chemistry | FuseSchool

Summary

The video script explains the significance of numbers on the periodic table. The atomic number (Z) indicates the number of protons in an element's atom, distinguishing elements from one another. The mass number (A) represents the sum of protons and neutrons. By knowing these numbers, one can calculate the number of neutrons in an atom. Examples given include Hydrogen with 1 proton and Oxygen with 8 protons, illustrating how to determine neutron count.

Takeaways

• 🔍 Each element on the periodic table has a unique box with two key numbers.
• 🔢 The atomic number (Z) represents the number of protons in an atom of an element.
• 🌐 The atomic number is consistent for all atoms of the same element but varies between different elements.
• 💡 Hydrogen has an atomic number of 1, indicating it has one proton, while Oxygen has an atomic number of 8, indicating it has eight protons.
• 📊 The mass number (A) signifies the total number of protons and neutrons in an atom.
• ⚖️ Protons and neutrons each have a relative mass of 1, and the mass of electrons is negligible in calculating the mass number.
• 🧠 The number of neutrons in an atom can be calculated using the formula: Neutrons = Mass Number - Atomic Number.
• 🌰 Oxygen, with a mass number of 16 and an atomic number of 8, has 8 neutrons (16 - 8 = 8).
• 🚀 Lithium, with a mass number of 7 and an atomic number of 3, has 4 neutrons (7 - 3 = 4).
• 🔑 Understanding atomic and mass numbers is crucial for distinguishing between elements and their isotopes.
• 📚 The periodic table is a fundamental tool in chemistry that organizes elements based on their atomic structure.

Q & A

What is the atomic number and what does it represent?

The atomic number, symbolized by 'z', represents the number of protons in the nucleus of an atom of a particular element. It is unique for each element and remains constant for all atoms of that element.

How does the atomic number differ between elements?

The atomic number differs between elements because each element has a unique number of protons. For example, hydrogen has an atomic number of 1, while oxygen has an atomic number of 8.

What is the mass number and what does it include?

The mass number, symbolized by 'A', represents the total number of protons and neutrons in the nucleus of an atom. It is a measure of the atomic mass, excluding the mass of electrons.

Why are electrons not considered in the mass number calculation?

Electrons are not considered in the mass number calculation because their mass is extremely small compared to that of protons and neutrons, and thus they do not significantly contribute to the atomic mass.

How can you calculate the number of neutrons in an atom?

You can calculate the number of neutrons in an atom by subtracting the atomic number from the mass number: Neutrons = Mass Number - Atomic Number.

What is the mass number of oxygen and how many neutrons does it have?

Oxygen has a mass number of 16 and an atomic number of 8, which means it has 8 neutrons (16 - 8 = 8).

What is the mass number of lithium and how many neutrons does it have?

Lithium has a mass number of 7 and an atomic number of 3, indicating it has 4 neutrons (7 - 3 = 4).

Why is the mass number always greater than or equal to the atomic number?

The mass number is always greater than or equal to the atomic number because it includes both the number of protons and neutrons, and neutrons add to the total atomic mass.

What is the significance of the atomic number in identifying an element?

The atomic number is significant in identifying an element because it is unique to each element and determines the element's position in the periodic table.

How does the number of protons affect the chemical properties of an element?

The number of protons, which is the atomic number, determines the element's chemical properties because it defines the number of electrons in the outer shell, which is crucial for chemical bonding and reactivity.

Can an element have different mass numbers while having the same atomic number?

Yes, an element can have different mass numbers due to the presence of isotopes, which are variants of the element with different numbers of neutrons but the same number of protons.

What is the relationship between the atomic number and the position of an element in the periodic table?

The atomic number directly corresponds to the position of an element in the periodic table, with elements arranged in increasing order of their atomic numbers from left to right and top to bottom.