BIOS 41 - Atoms

• Protons are positively charged particles found in the nucleus.
• Neutrons are neutral particles that have no charge and are found in the nucleus of an atom.
• Electrons are negatively charged particles that are found in the outer shell of an atom.
• Atomic number is the number of protons in an atom of an element.
• Atomic mass is the number of protons and neutrons in an atom.
• Atomic number determines what an element is.
• Atomic mass determines what version of an element is, also known as isotopes
• Electron shells (orbitals) can have multiple layers, and the outermost layer is the valence shell.
• Isotopes are elements with the same amount of protons but different numbers of neutrons.
• Ions are charged atoms with an uneven number of protons and electrons.
• Ions occur when electrons are transferred between atoms, and the atoms become charged.
• Ionic bonds form when 2 ions of opposite charges that attract.
• Ionic bonds form salts.
• Covalent bonds are two atoms that share electrons to fill their valence shell.
• Covalent bonds form molecules.
• The first shell of an atom can hold up to 2 electrons.
• The second shell of an atom can hold up to 8 electrons.
• Electronegativity is the strength of an atom's attraction for electrons.
• A chemical bond is when 2 atoms become linked to each other and form a new substance.
• The two types of chemical bonds are covalent bonds and ionic bonds.
• The 4 most common elements that make up most cells are carbon, hydrogen, oxygen, and nitrogen.
• Two reasons that some atoms are more reactive than others is:

  1. The electronegativity of the atom determines the reactiveness
  2. The number of electrons in the valence shell
• Hydrogen can form only 1 covalent bond
• Carbon can form 4 covalent bonds
• Nitrogen can form 3 covalent bonds
• Oxygen can form 2 covalent bonds
• Different uses for radioactive elements include smoke detectors, cancer treatment, generating energy, and determining the age of a fossil.
• What are the 4 most common elements that make up most cells?

  carbon, hydrogen, oxygen, nitrogen
• What are 2 reasons that some atoms are more reactive than others?

  The two types of chemical bonds are covalent bonds and ionic bonds