Atomic Number & Mass Number | Properties of Matter | Chemistry | FuseSchool
Summary
TLDRThe 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
🔍 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.
Mindmap
Keywords
💡Periodic Table
💡Atomic Number
💡Proton
💡Element
💡Mass Number
💡Neutron
💡Electron
💡Isotopes
💡Nuclear Structure
💡Chemical Properties
💡Calculation
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.
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