CHM 233 Lecture Notes - Lecture 2: Deuterium, Electronegativity, Ionic Bonding

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Published on 20 Sep 2015
School
ASU
Department
Chemistry
Course
CHM 233
Page:
of 5
CHM233 Lecture #2: Chapter 1: Remembering General Chemistry Electronic Structure and
Bonding
Atomic Structure
Protons and neutrons exist in the nucleus
o Dense part of the atom
Electrons exist in electrons clouds
Mass of the atom = Protons + Neutrons
Changing the number of protons changes the element
o 6 Protons is Carbon
o 7 Protons will be Nitrogen
Changing the number of neutrons
o Same element
o Different mass
o Results in Isotopes
Changing the number of electrons will alter the charge of the element
o Result in Ions
o Cations: more protons than electrons
Positively charged
o Anions: more electrons than protons
Negatively charged
Common Isotopes in Organic Chemistry
11H (Hydrogen)
21H (Deuterium, D)
31H (Tritium, T)
Protons
(atomic
number)
1
1
1
Neutrons
(A = Z -
N)
0
1
2
Electrons
(balance protons)
1
1
1
126C
136C
146C
Protons
(atomic
number)
6
6
6
Neutrons
(A = Z -
N)
6
7
8
Electrons
(balance protons)
6
6
6
Deuterium is often used for labeling positions
Deuterium and Carbon-13 will be seen in solvents in a technique called nuclear magnetic
resonance spectroscopy
Carbon-14 used commonly for archaeological discoveries - it allows to determine the age of
discovered items - a.k.a. radio dating.
Radio dating is taking the known half-life of an element and using it along with its natural
abundance and organisms to determine the age of an object.
Atomic Orbitals
4 major classification of atomic orbitals in electrons shells and are described using primary
quantum numbers - these are atomic orbitals, a.k.a. unhybridized
o S orbitals
First energy shell away from nucleus
Only s orbital
S subshell has one orbital and can only hold a maximum of two electrons
o P orbitals
Second energy shell away from nucleus
Both s and p orbitals
o D orbitals
Third energy shell away from the nucleus
Contains s, p; d orbitals
o F orbitals
Forth energy shell away from nucleus
Contains all s, p, d; f orbitals
Hybrid atomic orbitals - combination of orbitals in energy
Orbitals s, p, d; f are used to determine electron configuration for different elements
o Need to understand how the periodic table works for this
o Mainly focus on s and p orbitals and blocks for organic chemistry
Electron Configuration
Aufbau Principle - electrons always fill from lowest energy to highest energy
o Remove electrons from the highest to lowest energy level
Pauli Exclusion - only two electrons can fit in each orbital; they must have opposite spins
o Opposite spins to avoid having the same quantum number
Hund’s Rule - degenerate (same energy: px and py) orbitals will fill one electron at a time
Coefficient represents the energy shell or level; superscripted number represents electrons
Core electrons - inner, lower energy shells; typically not involved in reactivity
Valence electrons - outer, highest energy shells, number of e- is equal to main group; involved in
reactivity
Hydrogen: 1s1
Helium: 1s2
Lithium: 1s22s1
Carbon: 1s22s22p2
Chlorine: 1s22s22p63s23p5 or [Ne] 3s23p5
Core Electrons= 2 2 2 2 2 2 2 2
Valence Electrons=
1 2 3 4 5 6 7 8
Valence electrons must match main group numbers
Bonding
Bonding atoms together results in them having lower energy
o Having lower energy indicates higher stability which is goal in organic chemistry
Types of Bonds:
o Ionic bonds - formed between metals and nonmetals (electrostatic attraction)
The bonding happens due to extreme differences in electronegativity
One atom gives up an electron while the other uses it up without sharing
Isoelectronic - presents same electronic configurations to a noble gases
Less reactivity
Higher stability
Bond formation is always exothermic because it ends at a lower energy than the
beginning of the chemical formation/reaction
Li Li+ + 1e-
F + 1e- F-
o Covalent bonds - formed between the sharing of electrons amongst nonmetals
Hydrogen could behave as both a metal and nonmetal
H H HH
Electronegativity and Bond Polarity
Same electronegativity atoms, or those within .5 units of one another, are sharing electrons, the
sharing is considered equal
o Creates a nonpolar bond (equal distribution of electrons)
H2 Cl2 C - H
H - H Cl - Cl Nonpolar for organic
Nonpolar Nonpolar chemistry purposes.
Two atoms of different electronegativity sharing electrons have unequal sharing
o Creates a polar bond (unequal distribution of electrons)
o Polar covalent bond (slightly unequal distribution of electrons between two nonmetals)
Dipole bonds - has a positive and a negative end; they aren’t full charges
Symbolized by +δ and -δ
o Ionic bond - when one atom uses up all electrons (nonmetal) while another gives all its
electrons up (metals)
Li
Be
B
C
Ne

Document Summary

Chm233 lecture #2: chapter 1: remembering general chemistry electronic structure and. Protons and neutrons exist in the nucleus: dense part of the atom. Mass of the atom = protons + neutrons. Changing the number of protons changes the element: 6 protons is carbon, 7 protons will be nitrogen. Changing the number of neutrons: same element, different mass, results in isotopes. Changing the number of electrons will alter the charge of the element: result in ions, cations: more protons than electrons. Positively charged: anions: more electrons than protons. Deuterium is often used for labeling positions. Deuterium and carbon-13 will be seen in solvents in a technique called nuclear magnetic resonance spectroscopy. Carbon-14 used commonly for archaeological discoveries - it allows to determine the age of discovered items - a. k. a. radio dating. Radio dating is taking the known half-life of an element and using it along with its natural abundance and organisms to determine the age of an object.