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Topic 1 Basic Chemistry I. Atomic Theory of Matter A. Atoms, Elements, and Compounds 1. atoms – the basic building blocks of matter – cannot be subdivided by ordinary chemical means 2. elements – substances made of only one kind of atom – ex. oxygen, nitrogen 3. compounds – substance that contains two or more kinds of atoms in definite proportions – ex. water, salt B. Structure of atoms 1. nucleus – contains two types of subatomic particles – protons and neutrons a. proton – positively charged – the number of protons determines the atomic number – the number of protons is equal to the number of electrons in an atom that has no charge b. neutron – neutral (no charge) – the number of protons plus the number of neutrons is called the mass number 2. shells – electrons are found outside of the nucleus electrons have a negative charge and very little mass you will find two electrons in the first energy shell and eight in each shell after that not all the shells will be complete – if an atom has eight electrons in its outer shell it is said to be stable and is resistant to join with other atoms C. Isotopes – same element but with different numbers of neutrons – atomic number stays the same but mass numbers are different – many isotopes are radioactive II. Chemical bonding and chemical reactions A. Bonds – the formation of a compound involves either the transfer or sharing of electrons between atoms – this results in the formation of bonds – there are three types that we will focus on 1. ionic bonds – transfer of electrons – one atom becomes positive and the other becomes negative (ions) Ionic bonds – transfer of electrons 2. covalent bonds – sharing of electrons – sometimes the sharing of electrons is not equal and the covalent bond becomes known as polar covalent – one atom will become slightly negative and the other atom will become slightly positive Covalent bonds – share electrons – water is polar and methane is nonpolar Polar covalent bonds – electrons are not shared equally 3. hydrogen bonds - form when a hydrogen atom that is already covalently bonded to a strongly electronegative atom is attracted to another strongly electronegative atom Hydrogen bonds B. The strength of the force of attraction: 1. strongest – ionic bonds 2. second strongest – polar covalent bonds 3. third strongest – covalent bonds 4. weakest – hydrogen bonds C. Chemical formulas – shows which elements are found in a compound – two types 1. molecular formula – shows how many of each kind of atom are present in a molecule of a compound C6H12O6 2. structural formula – shows how the atoms of a molecule are bonded together D. Chemical Reactions – a chemical equation represents the results of a chemical reaction – matter is neither created nor destroyed – the reactants are on the left side of the equation and the products on the right side of the equation