Transcript - Chemistry
Chapter 5 Electrons in Atoms Dalton’s Model (1803) Atom are tiny indestructible objects (like marbles). Every element had a unique “marble”. Atoms could combine in fixed ratios. Thomson’s Model (1897) Atom has positive and negative parts. Most of atom is positive with negative particles spread out. Called a “plum pudding” model. Rutherford’s Model Rutherford’s Model (1911) • Discovered Discoveredthe thenucleus nucleus • Small dense and positive Very small and around in Electron cloud • Electrons moved positively charged Most of the atom is empty space with electrons moving around Bohr’s Model (1913) Electrons are in “rings” or energy levels. Energy separates one level from another. Electrons can never be found in between two levels. A quantum is the amount of energy needed to move from one energy level to the next. Like a ladder, every step up requires more energy. Unlike a ladder the “steps” of energy levels are uneven. The Modern Model (the Quantum Mechanical Model) More details about energy levels. All orbits are not sphere-shaped. It can only tell us the probability of finding an electron a certain distance from the nucleus. S orbitals There is one s orbital in every energy level Sphere shaped Each s orbital can hold 2 electrons Called the 1s, 2s, 3s, etc.. orbitals. p orbitals Start at the second energy level Peanut-shaped 3 different directions Each orbital can hold 2 electrons d orbitals Daisy shaped (except the 5th picture) 5 d orbitals can hold 10 electrons Each d orbital can hold 2 electrons f orbitals Start at the fourth energy level “Funny” shaped Seven orbitals (7 total= up to14 electrons) Electron Configurations Tells the way electrons are arranged in atoms. Gives more details than Bohr Electrons must fill in this order 1s22s22p63s23p64s23d104p65s24d105p6… Electron Configurations Lowest The energy fill first. energy levels overlap (ex: …4s23d104p6…) Electrons must fill the spaces in order and cannot leave any empty spaces before moving on. This is called the Aufbau Principle Orbital Notation Start 3d10 4s2 3p6 3s2 2p6 2s2 1s2 with electron configuration and add one box for every orbital. Show electrons by putting arrows in the boxes. (Pointing opposite ways.) Notice Orbital Notation in the last box the electrons spread out before doubling up. This is Hund’s Rule 3d10 4s2 3p6 3s2 2p6 2s2 1s2 Notice Orbital Notation that only the boxes of the last part (4d4) can have empty spaces. They have to be filled in order according to the Aufbau Principle 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d4 Pauli Exclusion Principle The 2 arrows have to point opposite ways. Two electrons in the same orbital (box) must be spinning in opposite directions according to Pauli 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d4