Chemistry Notes PDF

Created by Turbolearn AI Elements, Compounds, and Mixtures Elements, compounds, and mixtures are the building blocks of matter. Understanding the differences between them is crucial in chemistry. Elements An element is a pure substance made up of only one type of atom. Elements are repr...

Created by Turbolearn AI Elements, Compounds, and Mixtures Elements, compounds, and mixtures are the building blocks of matter. Understanding the differences between them is crucial in chemistry. Elements An element is a pure substance made up of only one type of atom. Elements are represented by chemical symbols, such as O for oxygen or H for hydrogen. There are about 118 known elements, each with its unique properties. Elements cannot be broken down into simpler substances. Compounds A compound is a substance formed when two or more different elements chemically combine. Compounds have distinct and unique properties different from the elements that make them up. Compounds can be represented by chemical formulas, such as H2O for water or CO2 for carbon dioxide. Compounds cannot be separated physically; chemical reactions are needed to break them into their individual elements. Mixtures A mixture is a combination of two or more substances that are physically mixed together but not chemically bonded. Mixtures can be separated by physical means, such as filtration or distillation. The components in a mixture retain their individual properties. Atoms, Molecules, and Compounds It's common to find the terms atom, molecule, and compound somewhat confusing. Here's a simplified explanation: Page 1  Created by Turbolearn AI Atom: The smallest indivisible unit of an element. Molecule: A group of atoms bonded together. Molecules can be made of atoms of the same or different elements. Compound: A specific type of molecule that consists of atoms of different elements chemically bonded together. Atomic Structure An atom is the smallest unit of matter that makes up everything around us. Atoms are the basic building blocks of all substances and come in different types known as elements. Subatomic Particles Particle Charge Mass Proton +1 1 atomic mass unit amu Neutron 0 1 amu Electron -1 approximately 1/1836 amu negligible Electron Shells Electrons are arranged in energy levels or electron shells around the nucleus. These shells can hold specific numbers of electrons, with the innermost shell having the lowest energy and subsequent shells having higher energy levels. Atomic Number and Mass Number Atomic Number Z : The number of protons in the nucleus of an atom. Mass Number A: The total number of protons and neutrons in the nucleus of an atom. The atomic number is represented by the symbol Z, and the mass number is represented by the symbol A. The atomic number is equal to the number of protons, which is also equal to the number of electrons in a neutral atom. Calculating the Number of Neutrons Page 2  Created by Turbolearn AI To find the number of neutrons in an atom, subtract the atomic number from the mass number: A - Z = number of neutrons For example, carbon-12 has a mass number of 12 and an atomic number of 6. Therefore, the number of neutrons is: 12 - 6 = 6 neutrons Page 3