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.

Outlines

00:00

🔍 Understanding Atomic and Mass Numbers

This paragraph explains the significance of atomic and mass numbers found on the periodic table. The atomic number, denoted by 'z', indicates the number of protons in an atom of an element, which is unique to each element. For instance, hydrogen has one proton, hence an atomic number of 1, while oxygen has 8 protons, giving it an atomic number of 8. The mass number, symbolized by 'A', represents the total number of protons and neutrons in an atom. Since electrons are negligible in mass, they are not considered in the mass number. The relationship between the mass number and atomic number allows us to calculate the number of neutrons in an atom: Neutrons = Mass Number - Atomic Number. The paragraph provides examples with oxygen, which has 8 neutrons (16 mass number - 8 atomic number), and lithium, which has 4 neutrons (7 mass number - 3 atomic number), to illustrate this concept.

Keywords

💡Periodic Table

The Periodic Table is a tabular arrangement of chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. It is the central theme of the video, as it serves as the visual reference for discussing atomic and mass numbers. The script explains that each element has its own box on the table, which contains key numerical identifiers for the elements.

💡Atomic Number

The atomic number, symbolized by 'Z', is defined as the number of protons in the nucleus of an atom. It is a unique identifier for each element, as the script illustrates with Hydrogen having an atomic number of 1 and Oxygen having an atomic number of 8. This concept is fundamental to the video's theme, as it differentiates elements from one another.

💡Proton

A proton is a subatomic particle with a positive electric charge, found in the nucleus of an atom. The script explains that the atomic number represents the count of protons, which is crucial for determining the element's identity. For example, Hydrogen's atomic number is 1, indicating it has one proton.

💡Element

An element is a pure substance consisting of only one type of atom, distinguished by its atomic number. The video script uses elements to demonstrate the concept of atomic and mass numbers, such as Hydrogen and Oxygen, which are fundamental to understanding the periodic table.

💡Mass Number

The mass number, symbolized by 'A', is the sum of the number of protons and neutrons in an atom's nucleus. The script explains that it is indicated in the element's box on the periodic table and is used to calculate the number of neutrons present in an atom, as shown with Oxygen's mass number of 16.

💡Neutron

A neutron is a subatomic particle with no electric charge, also located in the nucleus of an atom. The script clarifies that the mass number minus the atomic number equals the number of neutrons, which is essential for understanding atomic structure, as demonstrated with Oxygen having 8 neutrons.

💡Electron

Electrons are subatomic particles with a negative electric charge that orbit the nucleus of an atom. Although the script mentions that electrons are very light and their mass is not considered in the mass number, they are crucial for understanding atomic structure and chemical bonding.

💡Isotopes

Isotopes are variants of a particular chemical element which differ in neutron number. While the term 'isotopes' is not explicitly used in the script, the concept is implicit in the discussion of mass numbers and the calculation of neutrons, as different isotopes of an element will have the same atomic number but different mass numbers.

💡Nuclear Structure

Nuclear structure refers to the composition of an atom's nucleus, including the number of protons and neutrons. The script's explanation of atomic and mass numbers directly relates to understanding an atom's nuclear structure, as these numbers determine the types and quantities of subatomic particles within the nucleus.

💡Chemical Properties

Chemical properties are the characteristics that define how an element reacts with other substances. Although not explicitly detailed in the script, the atomic number, which determines an element's identity, is intrinsically linked to its chemical properties, as elements with the same number of protons exhibit similar behaviors.

💡Calculation

The script involves calculations to determine the number of neutrons in an atom by using the relationship between the atomic number and the mass number. This calculation is a practical application of the concepts discussed in the video, allowing viewers to understand how to derive one property (number of neutrons) from known values (atomic and mass numbers).

Highlights

Each element on the periodic table has its own box with two numbers: the atomic number and the mass number.

The atomic number (symbol 'Z') indicates the number of protons in an atom of an element.

All atoms of a particular element have the same atomic number.

Different elements have different atomic numbers, reflecting the varying number of protons.

Hydrogen has an atomic number of 1, indicating it has 1 proton.

Oxygen has an atomic number of 8, indicating it has 8 protons.

The mass number (symbol 'A') represents the total number of protons and neutrons in an atom.

Protons and neutrons each have a relative mass of 1, while electrons' mass is negligible for the mass number.

The number of neutrons in an atom can be calculated using the formula: Mass Number = Atomic Number + Number of Neutrons.

Oxygen with a mass number of 16 and atomic number 8 has 8 neutrons (16 - 8 = 8).

Lithium with a mass number of 7 and atomic number 3 has 4 neutrons (7 - 3 = 4).

The atomic number is the count of protons in an atom.

The mass number is the combined count of protons and neutrons in an atom.

Understanding atomic and mass numbers is crucial for grasping the composition of elements.

The mass number minus the atomic number gives the number of neutrons, providing insight into an atom's structure.

These concepts are fundamental to the study of chemistry and the periodic table.

The relationship between atomic number, mass number, and neutrons is essential for understanding atomic structure.

Transcripts

When you look at the periodic table you will see that each element has its own box, and

within that box, you will find two numbers. The atomic number, or proton number, and the

mass number, but what do these numbers mean? The atomic number has the symbol 'z',

this number tells you how many protons are in one atom of an element. The number is always

the same for all atoms of a particular element. Atoms of different elements have different

atomic numbers, meaning they have different numbers of protons.

For example, an atom of Hydrogen has an atomic number of 1 because it has 1 proton, but an

atom of Oxygen has and atomic number of 8 because it has 8 protons.

The next number we look at is the mass number. The mass number has the symbol A.

This mass number tells you how many protons AND neutrons are in one atom of an element.

We need to remember that Protons and Neutrons each have a relative mass of 1 and that Electrons

are so small, that their mass does not need to considered in the mass number of an atom.

So if we know the mass number of an element, and we know the atomic number we can calculate

the number of Neutrons in an atom of a particular element.

So the Mass Number = The Atomic Number + the Number of Neutrons

Mass Number = protons + neutrons So if we take oxygen,

Oxygen has a mass number of 16 and an atomic mass of 8, how many neutrons does it have?

Remember Mass Number = protons + neutrons We can rearrange this to show that

Neutrons = Mass Number -- Atomic Number Neutrons = 16 -- 8

= 8 Oxygen therefore has 8 neutrons.

Let take another example,

Lithium has a mass number of 7 and an atomic mass of 3, how many neutrons does it have?

Mass Number = protons + neutrons We can rearrange this to show that

Neutrons = Mass Number -- Atomic Number Neutrons = 7- 3

= 4 Lithium therefore has 4 neutrons.

So the atomic number is the number of protons in an atom and the mass number is the number

of protons and neutrons in an atom.