NEM 10V Lecture Notes - Lecture 4: Hydrogen Bond, Nematology, Chemical Polarity

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6 May 2018

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Nematology

Part 4: Water Part 1

• Atoms-fundamental unit of matter, made of 3 subatomic particles:

-Protons +

-Electrons –

-Neutrons 0

-Protons & neutrons located in the nucleus at the center of an atom

-Electrons orbit nucleus

-Protons identifies element

-Rings/orbitals are used to illustrate the number of electrons at different energy

states surrounding the nucleus

-Only electrons at the highest energy states or outermost orbital participate in

chemical reactions. These are called valence electrons and they are involved in

the formation of chemical bonds between atoms.

-Outer shell of atoms holds 8 electrons. -chemically stable

-Octet Rule-when atoms combine to form compounds they can give up, accept,

or share electrons to achieve an octet of electrons in their outer shells

-Covalent bond is formed when atoms share electrons in order to satisfy the octet

rule. Carbon has 4 electrons in its outer shell but can share electrons to complete

the outer shell.

-Example, 1 carbon and 4 hydrogen atoms, achieves an octet of electrons.

Hydrogen achieves 2 electrons in its outer shell and is stable.

-Ionic bonds forms when atoms are held together by the attraction between

opposite charges. Charged atoms are called ions. Ions of opposite charge attract

each other and form ionic bonds.

• Because atoms differ in their electronegativity, atoms forming covalent bonds do

not always share their electrons equally.

• Electronegativity is the ability to attract electrons. Atoms with high

electronegativity strongly attract electrons. Atoms with low electronegativity do

not pull at the electrons as much.

• Carbon and Hydrogen have similar electronegativity values. When C and H are

bonded together, both atoms have a similar ability to attract electrons. This type

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Document Summary

Part 4: water part 1: atoms-fundamental unit of matter, made of 3 subatomic particles: Protons & neutrons located in the nucleus at the center of an atom. Rings/orbitals are used to illustrate the number of electrons at different energy states surrounding the nucleus. Only electrons at the highest energy states or outermost orbital participate in chemical reactions. These are called valence electrons and they are involved in the formation of chemical bonds between atoms. Octet rule-when atoms combine to form compounds they can give up, accept, or share electrons to achieve an octet of electrons in their outer shells. Covalent bond is formed when atoms share electrons in order to satisfy the octet rule. Carbon has 4 electrons in its outer shell but can share electrons to complete the outer shell. Example, 1 carbon and 4 hydrogen atoms, achieves an octet of electrons. Hydrogen achieves 2 electrons in its outer shell and is stable.

Related Questions

A covalent chemical bond is one in which:

A. Outer shell electrons are shared by two atoms so as to satisfactorily fill the outer electron shells of both.

B. Outer shell electrons of one atom are transferred to the inner electron shells of another atom.

C. Protons or neutrons are shared by two atoms so as to satisfy the requirements of both.

D. Electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged

brownantelope470

One facet of the central field approximation for many-electronatoms is that inner-shell electrons screen the nuclear charge. Tounderstand how this works quantitatively, first note that theprobability distributions for electrons in different shellsgenerally do not overlap much. For instance, the electrons in the Mshell (n=3) are almost always farther from the nucleus than theelectrons of the K (n=1) and L (n=2) shells. Thus, it is a goodapproximation to assume that the inner shells completely screen thenucleus from the outer shells. For example, if there are tenelectrons altogether in the K and L shells of an atom, then theelectrons in the M shell experience force from a charge of roughlyZ-10, where Z is the charge on the nucleus as an integer multipleof e, the magnitude of the charge on an electron. This is calledthe effective nuclear charge Z_eff.

a. In a beryllium atom (Z=4), how many electrons are in the Kshell?
Express your answer as an integer.

b. n xenon (Z=54), what is the effective charge Z_eff experiencedby an electron in the M (n=3) shell?
Express your answer as an integer.

c. How many electrons are there altogether in the K, L, and Mshells of xenon? Recall that for n=3, the orbital quantum number lmust be zero, one, or two and that m_l can take any value betweenpostive and negative l.
Express your answer as an integer.

d.

The idea of simply subtracting the number of inner-shell electronsworks well only for atoms with low values of Z. For atoms withlarger nuclear charge, the different shapes of the probabilitydistributions for different subshells becomes an important factor.For instance, in the N shell, electrons in the s subshell have amuch higher probability than those in the p or d subshells of beingfound closer to the nucleus than some of the K, L, or M electrons.It is said that the s electrons penetrate the inner shells morereadily than do the p or d electrons. Therefore, it is to beexpected that our simple subtraction model may not work well forouter-shell s electrons in large atoms. Keeping this in mind, wesee that the effective nuclear charge Z_eff for the outermostelectron in an atom may be found experimentally by measuring theionization energy of an atom and then calculating the effectivecharge using the equation

E_n=- \frac{Z_{\rm eff}^2}{n^2}(13.6\;\rm eV).

The energy for the 5p valence electron in indium (Z=49) is -5.79electron volts. What is the effective nuclear charge Z_effexperienced by this electron?
Express your answer to three significant figures.

NEM 10V Lecture Notes - Lecture 4: Hydrogen Bond, Nematology, Chemical Polarity

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