The Periodic Table & Electronic Structure

Transcription

1 Periodic Table The Periodic Table & Electronic Structure Is there an overall reason that the elements are arranged in the order that they are? Yes! We ve seen that the elements are arranged in order of an Element s properties. Periodic Table Electronic Structure is one of an element s properties. The Electronic Structure is based on where the electrons are located. The electrons are located in: ENERGY LEVELS and SUBLEVELS. Periodic Table Electronic Structure is the address of the electrons in an atom. David can be found at: 1118 E. 4th St Oxygen can be found at: 1s 2 2s 2 2p 4 Beryllium can be found at: 1s 2 2s 2 Magnesium can be found at: 1s 2 2s 2 2p 6 3s 2

2 Periodic Table Periodic Table The electrons are located in ENERGY LEVELS and SUBLEVELS. Energy Levels are:! 1, 2, 3, 4, 5, 6, 7 You can tell the Energy Levels and Sublevels being used by looking at the Periodic Table, (your friend). Sublevels are: s, p, d, f # of orbitals: # of electrons: I II! III IV V VI VII VIII The Periodic Table is divided into sections based on the number of electrons that each sublevel can hold. On a blank piece of paper, draw this periodic table. (n) is the ENERGY LEVEL

3 Writing Electronic Structures The Rules Energy levels fill up one after another. 1 2 The # electrons = # protons (For atoms with no positive or negative charge) Some examples: H 1 s 1 He Li 1 s 2 1 s 2 2 s 1 Be 1 s 2 2 s 2 The exponents used must add up to the Atomic Number of the atom for neutral atoms (atoms that have no electrical charge). He 1s 2 Atomic # is 2 Some more examples: Be 1 s 2 2 s 2 B 1 s 2 2 s 2 2 p 1 C 1 s 2 2 s 2 2 p 2 N 1 s 2 2 s 2 2 p 3 O F Ne Na 1 s 2 2 s 2 1 s 2 2 s 2 1 s 2 2 s 2 1 s 2 2 s 2 2 p 4 2 p 5 2 p 6 2 p 6 3 s 1

4 Did you see the pattern in the previous examples?! The Noble Gas that ends the previous row, contains all of the electrons that the elements in the next row start with.! You can use the symbol of the previous Noble Gas as a shortcut in writing an subsequent element s electronic structure. Ne! 1s 2 2s 2 2p 6 Al! 1s 2 2s 2 2p 6 3s 2 3p 1 becomes Al! [Ne] 3s 2 3p 1 Row 3 looks like: Na! [Ne] 3s 1 Mg! [Ne] 3s 2 Al! [Ne] 3s 2 3p 1 Si!! [Ne] 3s 2 3p 2 P!! [Ne] 3s 2 3p 3 S!! [Ne] 3s 2 3p 4 Cl! [Ne] 3s 2 3p 5 Ar! [Ne] 3s 2 3p 6 The exponents used must add up to the Atomic Number of the atom for neutral atoms (atoms that have no electrical charge). Li 1 s 2 2 s 1 So remember the Order of Filling for each row: Negatively charged atoms have MORE electrons than the atom s Atomic Number. Li 1-1 s 2 2 s 2 Positive charged atoms have LESS electrons than the atom s Atomic Number. Li 1+ 1 s 2

5 More about sublevels and their orbitals. Each sublevel can hold only a specific number of electrons. What does an s orbital look like? These electrons are located in orbitals, which is the specific location for the electrons within a sublevel. Orbital holding capacities. Sublevel Orbital # of electrons s 1 2 p 3 6 d 5 10 f 7 14 What does the p orbital look like? How do we know that these energy levels, sublevels and orbitals exist?

6 So that s the story, Atoms exist, they have structure, this structure can be imaged, used and is proven to exist! Now it s time to Practice! Electron Configuration The Quantum Numbers The Quantum Numbers More about Quantum Numbers Quantum numbers are locators, which describe each e - about the nucleus in terms of relative energy and probable location. n õ mõ locates each electron in a specific main energy level about the nucleus. locates the electron in a sublevel within the main shell. locates the electron in a specific orbital within the sublevel.

7 Locator Value 1 - n Quantum Number Locator Value 2 - õ Quantum Number n, the Principal quantum number: Has all integer values 1 to infinity: 1,2,3,4,... Locates the electron in an orbital in a main energy level about the nucleus, like Bohr s orbits. describes maximum occupancy of shell, 2n 2. The higher the n number: the larger the energy level the farther from the nucleus the higher the energy of the orbital in the energy level. locates electrons in a subevel region within the main energy level. limits number of sublevels to a value equal to n (1 in 1st shell, 2 in 2nd shell, 3 in 3rd shell etc) only four types of sublevels are found to be occupied in unexcited, ground state of atom These sublevel types are known by letter: s p d f Locator Value 2 - õ Quantum Number Locator Value 2 - õ Quantum Number n = 7 n = 6 n = 5 7s (7p 7d 7f 7g 7h 7i) 6s 6p 6d (6f 6g 6h) 5s 5p 5d 5f (5g) Highest, biggest And More About õ : AS WELL AS LOCATION, this Q# is quite important in describing a relative energy value for each of these regions, and the shape of each orbital in the sublevel. n = 4 4s 4p 4d 4f n = 3 n = 2 3s 3p 3d 2s 2p The l Q# distinguishes between the sublevels in terms of energy, s <p <d <f n = 1 1s Lowest energy, smallest level We will see shortly that each sublevels type, s, p, d, f contain orbitals of unique shape.

8 Locator Value 3 - mõ Quantum Number Locator Value 3 - m l Quantum Number mõ, the third quantum number, specifies in which orbital within a sublevel an electron may be found. It turns out that each sublevel type contains a unique number of orbitals, all of the same shape and energy. This third number completes the description of where a electron is likely to be found around the nucleus: The m l number describes an orbital within the region. This third number completes the description of where a electron is likely to be found around the nucleus. Locator Value 3 - m l Quantum Number The Quantum Number s m l values will describe the number of orbitals within a subshell, and give each orbital its own unique address : s sublevel p sublevel d sublevel f sublevel 1 orbital 3 orbitals 5 orbitals 7 orbitals All electrons can be located in an orbital within a sublevel within a main energy level. To find that electron one need a locating value for each: the n number describes an energy level (1,2,3...) the l number describes a sublevel region (s,p,d,f...) the m l number describes an orbital within the region

9 So that s the story, Atoms exist, they have structure, this structure can be imaged, used and is proven to exist! Now it s time to Practice! Nature of Light 2