ATOMIC MODELS AND ELECTRON BEHAVIOR Chelsea I Academic Chemistry
Proposed by Neils Bohr, a Danish physicist in 1913 Hydrogen atoms have energy states, the lowest state being the ground state (n=1) When an atom gains energy it moves from the ground state to an excited state (n=2) In the Bohr model there s a central nucleus with the electron orbiting in a circular motion A smaller orbit corresponds with a lower atomic energy state. While a higher energy state shows a larger electron orbit THE BOHR MODEL
THE QUANTUM MODEL Proposed by Louis de Broglie in 1924 Replaced the Bohr model and accounted for elements other than hydrogen Introduced the idea that electrons do not move in circular orbits around the nucleus Heisenberg uncertainty principle- It is fundamentally impossible to know precisely both the velocity and position of a particle at the same time. Electrons as waves
ATOMIC ORBITALS Atomic orbital- 3D region around nucleus. Predicts electron s probable location, but orbitals are not exactly defined. Quantum model assigns four quantum numbers to the orbitals. The first is the principle quantum number (n), which gives the relative size and energy of atomic orbitals. A larger n signifies a larger orbital, the electron spends more time away from the nucleus, and leads to a higher atomic energy. n values range from 1 to 7 (energy sublevels).
ATOMIC ORBITAL SHAPES Sublevels: s, p, d, f s (spherical), p(dumbbell shape) Each orbital house 2 electrons n=1 1s orbital n=2 2s, 2p (2px, 2py, 2pz) n=3 3s, 3p, 3d (3dxy, 3dxz, 3dyz, 3dz²*) x, y, z are different orientations n=4 includes 4f sublevel Complex, multiple lobes *different orientation and shape
ELECTRON CONFIGURATION The arrangement of electrons in an atom Follows: Aufbau principle- electrons are found in the lowest energy orbital available Pauli Exclusion principle- 2 electrons maximum for a single atomic orbital, have opposite spin Hund s rule- single electrons with same spin have to occupy each orbital before electrons with opposite spin can occupy the same one
ELECTRON CONFIGURATION AND THE PERIODIC TABLE Ex. Phosphorus: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Carbon: 1s 2 2s 2 2p 6 3s 2 3p 5 Hydrogen: 1s 2 The table is arranged in periods (rows) and groups (columns) according to electron configuration The seven periods represent the principal quantum numbers (n= 1to n= 7) Elements arranged by increasing atomic number In a period, each element has one more electron and proton than the element on its left The groups are separated by number of valence electrons. For example, Group I has a configuration of s 1, Group 2= s 2, etc Group I, 2, 13-18 have valence electrons in the s or p subshells Group 3-12, including the transition metals have their valence electrons in the s, d (and f) subshells.
ELECTRON CONFIGURATION AND CHEMICAL PROPERTIES Atom have the same chemical properties if they have the same number of valence electrons Ex. Group I, the alkali metals all have 1 valence electron This affects bonds between atoms Ionic Ratio- between cation (+) and anion (-) Ex. SrCl2, 1 Sr binds to 2 Cl2 Each atom has a specific number of bonds it can make
ELECTRON CONFIGURATION AND CHEMICAL PROPERTIES CONT. Covalent Combining capacity- Number of electrons it has to gain or lose in order to form stable octet (8 valence electrons in outer shell) Ionization energy- energy required to remove an electron Loss of electrons can allow atom to form bonds with other atoms Electronegativity- how much attraction an atom exerts on an electron in a chemical bond Atomic Radius-The distance between adjacent nuclei of identical atoms
PERIODIC TRENDS In a period, Ionization energy increases from bottom to top, electro negativity increases bottom to top, and atomic radius increases from top to bottom In groups, Ionization energy increases from left to right, electronegativity increases from left to right, and atomic radius increases from right to left.
COMPARISON BETWEEN A METAL, HALOGEN, AND NOBLE GAS The chosen alkali metal is Phosphorus (P), the chosen halogen is Carbon (C), and the chosen noble gas is Hydrogen (H).
BOHR MODEL OF AN ALKALI METAL, HALOGEN AND NOBLE GAS ATOM Phosphorus (P), Alkali metal Carbon (C), Halogen Hydrogen (H), Noble gas
Phosphorus (P), Alkali metal Carbon (C), Halogen Hydrogen (H), Noble gas Similarities: All three elements have outer shells Phosphorus, carbon, hydrogen have 2 electrons in the first outer shell Differences: Carbon and phosphorus have multiple shells (4 and 3, respectively) while hydrogen only has one Phosphorus has one more electron than carbon, while hydrogen only has 2 electrons in total
QUANTUM MODEL OF PHOSPHORUS, CARBON, AND HYDROGEN Hydrogen: 1s 2 Carbon: 1s 2 2s 2 2p 6 3s 2 3p 5 Phosphorus: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1
Hydrogen: 1s 2 Carbon: 1s 2 2s 2 2p 6 3s 2 3p 5 Phosphorus: 1s 2 2s 2 2p 6 3s 2 3p 6 Similarities: All three elements have at least one s orbital represented by the spherical shape Carbon and phosphorus have multiple, overlapping lobes 4s 1 Differences: Carbon and Phosphorus shows additional orbitals: 2s,2p, 3s, (K + shows 4s), while hydrogen only has its single 1s orbital Carbon is the only element that has an unpaired electron in the 3p orbital, while Phosphorus lacks one in the 4s shell
ELECTRON CONFIGURATION: AUFBAU DIAGRAM OF HYDROGEN Hydrogen: 1s 2
ELECTRON CONFIGURATION: AUFBAU DIAGRAM OF CARBON Carbon: 1s 2 2s 2 2p 6 3s 2 3p 5
ELECTRON CONFIGURATION: AUFBAU DIAGRAM OF PHOSPHORUS Phosphorus: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1
Similarities: Each element has at least one full box with 2 electrons in opposite spin Both carbon and phosphorus have an unpaired electron Differences: Phosphorus has more energy than carbon, carbon has more energy than hydrogen Hydrogen has a full outer shell and because of this, it s considered a noble gas
CHEMICAL PROPERTIES- BONDING TO OXYGEN AND CHLORINE Bonding to oxygen Phosphorus: P2-O Ionic bond: metal (cation)/nonmetal (anion) Carbon: C-O Covalent bond: sharing of electrons Hydrogen: He-O Does not bind to oxygen, since it is an inert gas Bonding to Chlorine Phosphorus: K-Cl Ionic bond: metal (cation)/nonmetal (anion) Carbon: C-Cl Covalent bond: equal sharing of electrons Hydrogen: He-Cl Does not bind to chlorine, since it is an inert gas
CHEMICAL PROPERTIES-COVALENT BONDS AND VALENCE ELECTRONS Number of covalent bonds element can form Phosphorus: 0 (only ionic) Carbon: 1 Hydrogen: 0 (no bonding) Number of valence electrons each element contains: Phosphorus: 1 Carbon: 7 Hydrogen: 2
CHEMICAL PROPERTIES-REACTIVITY, IONIZATION ENERGY, ELECTRONEGATIVITY Reactivity- How open to chemical reactions a compound is. Phosphorus: Very reactive Carbon: Reactive Hydrogen: Unreactive Ionization Energy Phosphorus only requires a small amount of energy to remove outermost electron Carbon requires a lot of energy to remove one of the valence electrons Hydrogen are neutral, it would take a large amount of energy to remove one of the valence electrons Electronegativity Phosphorus s electronegativity is low because it cannot attract electrons as well as elements from other groups Carbon have a strong attractive force for electrons, because they want to complete their outer shell to form an octet Hydrogen has very low electronegativity, because it cannot exert attractive forces on free electrons Atomic Radius- Distance between nucleus and surrounding electron cloud Phosphorus- Large Carbon- Small Hydrogen- Very small
PLACEMENT OF POTASSIUM, CHLORINE, AND HELIUM ON PERIODIC TABLE
PLACEMENT OF PHOSPHORUS, CARBON, AND HYDROGEN ON PERIODIC TABLE Phosphorus is in Group 1, Period 4: Group 1 elements all have 1 valence electron Large atomic radius Low electronegativity Low ionization energy Carbon is in Group 17, Period 3: Group 17 elements have 7 valence electrons Small atomic radius High electronegativity High ionization energy Hydrogen is in Group 18, Period 1 Noble Gas have full outer shells Very small atomic radius Extremely low electronegativity High ionization energy
PREDICTING CHEMICAL PROPERTIES OF ELEMENTS 85,86,87 As was stated before, elements in the same group share the same properties. These properties allow for a system to be put in place that would allow us to indentify the properties of an element only based on its location on the periodic table.
THE METHOD Does it combine with oxygen and chlorine? Yes Is it an ionic bond? Is it a covalent bond? No No bond can be formed, it is inert.
THE METHOD How many bonds does it form? Zero One Number of valence electrons One Less than 8 8 or more
THE METHOD If: can bond to oxygen and chlorine, bond is ionic, zero covalent bonds present, one valence electron present Then: Reactivity- very reactive Ionization energy- requires a small amount of energy Electronegativity- low Atomic radius- large Element is in group 1 If: can bond to oxygen and chlorine, bond is covalent, 1 covalent bond present, 7 valence electrons present Then: Reactivity- reactive Ionization energy- requires a lot Electronegativity- strong attractive force Atomic radius- small Element is in group 17
THE METHOD If: cannot bond to oxygen and chlorine, no ionic or covalent bond present, full set of valence electrons present (2 or 8) Then: Reactivity- unreactive Ionization energy- requires a large amount of energy Electronegativity- very low Atomic radius- very small Element is in group 18
ELEMENT 85 It is in group 17, period 6. Therefore it is expected to be similar to carbon (group 17, period 3) Nonmetal, element 85 should bind with oxygen and chlorine through covalent bonding. Should form at least 1 covalent bond. Presumed to have 7 valence electrons. Predicted chemical properties: it is reactive, requires large amount of energy to remove outermost electron, has a strong attractive force for electrons because it wants to form an octet, should have a small atomic radius. Element 85= Halogen (Astatine)
ELEMENT 86 It is in group 18, period 6. Therefore it is expected to be similar to hydrogen(group 18, period 1) Inert gas, element 86 should not bind with oxygen or chlorine through covalent or ionic bonding. Presumed to have 8 valence electrons, a stable octet. Predicted chemical properties: it is unreactive, requires a large amount of energy to remove outermost electron, has very low electronegativity because it cannot exert force on free electrons, should have a very small atomic radius. Element 86=Noble gas (Radon)
ELEMENT 87 It is in group 1, period 7. Therefore it is expected to be similar to phosphorus(group 1, period 4) Metal, element 87 should bind with oxygen and chlorine through ionic bonding. Doesn t form covalent bonds. Presumed to have 1 valence electron. Predicted chemical properties: it is very reactive, requires small amount of energy to remove outermost electron, has low electronegativity, should have a large atomic radius. Element 87= Alkali metal (Francium)
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