Intro to Chemistry

Intro to Chemistry Atoms and Molecules A molecule is a group of atoms bonded together by covalent bonds. An atom, on the other hand, is the smallest particle of an element that still retains its chemical properties. Subatomic Particles The three basic subatomic particles are protons, neutrons, and electrons. Protons and neutrons are found inside the nucleus of an atom, while electrons orbit around it. Charged Subatomic Particles Electrons have a negative charge, while protons have a positive charge. Neutrons have no charge or are neutral. Isotopes Isotopes are variations of an element that differ in the number of neutrons in their nucleus. For example, carbon-12, carbon-13, and carbon-14 are all isotopes of carbon. Atomic Mass Unit The atomic mass unit (amu) is a measurement used to determine the mass of an atom, equal to the mass of a single proton. Ion Formation An atom that gains an electron becomes a negatively charged ion, while an atom that loses an electron becomes a positively charged ion. Determining Number of Neutrons To find the number of neutrons in an atom, subtract the atomic number from the atomic mass. Atomic Number and Number of Electrons The number of electrons in a neutral atom is equal to the atomic number. The atomic number represents the number of protons in an atom. Element Ordering on the Periodic Table Elements are placed in order on the periodic table according to their atomic number, which is the number of protons in an atom. Periodic Table Components The vertical columns on the periodic table are called groups or families, while the horizontal rows are called periods. Group Properties All members of a group on the periodic table have the same number of electrons in their outermost energy level, leading to similar chemical properties. Finding Atomic Information Using the periodic table, we can find that chromium has 24 protons and 28 neutrons. All elements in the same period have the same number of energy levels.