MOLEKUL & ION - IPA SMP KELAS 9 - SEMESTER 2 - KURIKULUM 2013 - YASA

Summary

This educational video explains the concepts of molecules and ions, starting with a review of atoms. It describes molecules as combinations of two or more atoms, distinguishing between elemental molecules (e.g., O2, N2) and compound molecules (e.g., H2O, CO2). The video covers how to interpret chemical formulas and count atoms within molecules. Additionally, it introduces ions, both anions (negatively charged) and cations (positively charged), explaining how they form through electron gain or loss. The script also explains how to determine the number of protons, electrons, and neutrons in ions, providing clear examples.

Takeaways

• 😀 Molecules are combinations of two or more atoms, which can be of the same type or different types.
• 😀 Molecules are divided into two categories: element molecules (molecules made of identical atoms) and compound molecules (molecules made of different types of atoms).
• 😀 Examples of element molecules include oxygen (O2), nitrogen (N2), and sulfur (S8).
• 😀 Examples of compound molecules include water (H2O), carbon dioxide (CO2), and sodium chloride (NaCl).
• 😀 A chemical formula represents the number and type of atoms in a molecule, such as N2 for nitrogen or H2O for water.
• 😀 To determine the total number of atoms in a compound, you multiply the subscript in the chemical formula by the number of molecules. For example, 2H2O means 2 molecules of water, which contain 4 hydrogen atoms and 2 oxygen atoms.
• 😀 An ion is an atom or group of atoms that has a charge due to the loss or gain of electrons.
• 😀 Ions are classified into two types: anions (negative ions) and cations (positive ions). Anions gain electrons, while cations lose electrons.
• 😀 Example of an anion: Sulfur atom gains two electrons to become sulfide ion (S2-).
• 😀 Example of a cation: Barium atom loses two electrons to become barium ion (Ba2+).
• 😀 To determine the number of protons, electrons, and neutrons in an ion, consider the ion's charge and atomic number. For example, in Cl- (chlorine anion), the proton count is 17 (atomic number), and the electron count is 18 (since it gained one electron).

Q & A

What is the difference between molecules and ions?

Molecules are made up of two or more atoms bonded together, while ions are atoms or groups of atoms that have gained or lost electrons, resulting in a charged species.

How are molecules classified?

Molecules are classified into two types: elemental molecules (composed of atoms of the same element) and compound molecules (composed of atoms from different elements).

What is an example of an elemental molecule?

An example of an elemental molecule is oxygen (O2), which consists of two oxygen atoms bonded together.

What is an example of a compound molecule?

An example of a compound molecule is water (H2O), which is formed from hydrogen and oxygen atoms.

How do you read chemical formulas like 2N2 or H2O?

The number before the molecule (e.g., 2 in 2N2) indicates how many molecules of that substance are present, while the subscript in the formula (e.g., N2) shows how many atoms of each element are in one molecule.

How do you calculate the number of atoms in a compound?

To calculate the number of atoms in a compound, multiply the number of molecules by the number of atoms of each element present in one molecule. For example, 2H2O contains 4 hydrogen atoms and 2 oxygen atoms.

What are anions and cations?

Anions are negatively charged ions that gain electrons, while cations are positively charged ions that lose electrons.

How does a sulfur atom become an ion?

A sulfur atom becomes an ion by gaining two electrons, forming the sulfide ion (S2-), which carries a 2-negative charge.

What is an example of a cation?

An example of a cation is the barium ion (Ba2+), which forms when a barium atom loses two electrons.

How can you determine the number of protons, electrons, and neutrons in an ion?

To find the number of protons, refer to the atomic number of the element. For electrons, adjust the number based on whether the ion is positive or negative. Neutrons are calculated by subtracting the atomic number from the atomic mass.