Topic 1: the atom Flashcards
Dalton’s model
- elements are made of atoms
- atoms of an element are the same
- compounds are formed with combinations of atoms
Rutherford Experiment
Bombarded gold foil with alpha particles. some went through foil but some bounced off of nucleus. Found…
1. Atoms are mostly empty space
2. Nucleus is positively charged and dense
Bohr model
- Electrons surround the nucleus in circular orbits, the farther from the nucleus, the more energy
- Energy is needed for electrons to move to outer orbits
- Energy is emitted (as light) when electrons move back to ground state
Wave-mechanical model (Modern theory)
- Small, dense, positively charged nucleus
- Nucleus surrounded by electron cloud
- Orbitals- areas where an electron with a certain amount of energy is LIKELY to be found
Charge of protons, neutrons, and electrons
Protons= positive charge
Neutrons= no charge
Electrons= negative charge
Every atom has the same amount of protons and electrons, and therefore a charge of 0 (neutral).
Mass of protons, neutrons, and electrons
Proton= 1 amu
Neutron= 1 amu
Electron= 0 amu (almost)
What is amu?
1/12 the mass of a carbon atom
Atomic mass
Mass of an atom which is equal to the total number of neutrons and protons (each 1 amu)
Ground state vs excited state
Ground state= lowest possible energy state
Excited state= when gaining a specific amount of energy, an electron moves to a higher orbital
2-7 to 2-6-1
What happens when an electron moves from a higher energy state to a lower energy state?
Emits a specific amount of energy, usually in the form of LIGHT. This light can be measured (bright line spectrum) and used to identify an element (with a spectroscope).
How do valence electrons affect the chemical properties of an element?
- Atoms with filled valence shell are stable
- Atoms form bonds to fill their valence shells
