2. Atoms, Elements & Compounds (Part 1) (1/4) (Cambridge IGCSE Chemistry 0620 for 2023, 2024 & 2025)
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Elements are pure substances represented by symbols like O for oxygen, compounds are formed when elements combine chemically into unique substances like H2O, and mixtures are physically combined without chemical bonding like saltwater. Atoms are the smallest units of matter with protons, neutrons, and electrons, identified by atomic number and mass number used to locate elements on the periodic table, while relative atomic mass is the average mass of all isotopes rounded to the nearest whole number, helping to calculate the number of neutrons in an atom.
Insights
- Elements are substances made of one type of atom, like oxygen (O), and cannot be broken down further. Compounds form when different elements combine chemically, creating new properties. Mixtures, on the other hand, are physically combined but retain individual properties and can be separated.
- Atoms are the smallest units of matter, composed of protons, neutrons, and electrons. The atomic number signifies the protons in an atom, while the mass number is the sum of protons and neutrons. Understanding relative atomic mass aids in approximating the mass number, crucial in identifying elements accurately.
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What are elements?
Pure substances made of one type of atom.
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Summary
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"Elements, Compounds, Mixtures, Atoms: Basics Explained"
- Elements are pure substances made of one type of atom, represented by chemical symbols like O for oxygen. There are about 118 known elements, each with unique properties, and they cannot be broken down into simpler substances.
- Compounds are formed when different elements chemically combine, having distinct properties from the elements they're made of. They are represented by chemical formulas like H2O for water. Compounds cannot be separated physically and require chemical reactions to break them down.
- Mixtures are combinations of elements or compounds physically mixed but not chemically bonded. Components retain individual properties and can be separated physically, like saltwater. Elements, compounds, and mixtures have distinct characteristics and behaviors.
- Atoms are the smallest units of matter, consisting of a nucleus with protons and neutrons, and electrons orbiting in energy levels. Protons are positively charged, neutrons are neutral, and electrons are negatively charged. Atoms are identified by their atomic number and mass number.
- The atomic number represents the number of protons in an atom, equal to the number of electrons in a neutral atom. It helps locate elements on the periodic table. The mass number is the total of protons and neutrons in an atom's nucleus, determining the atom's mass.
- Relative atomic mass is the average mass of all isotopes of an element, often rounded to the nearest whole number. It can be used as a substitute for the mass number in most cases. Neutrons in an atom can be calculated by subtracting the number of protons from the mass number.
