All Things Covalent

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QUIZ Topics: Lewis Structures, Resonance Structures, Formal Charge and Properties of Covalent Molecules

Chemistry

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31 Terms

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Central atom

Atom in the center of the lewis structure, forms most bonds, is the least EN (NEVER H)

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How to know a central atom in a lewis structure

USUALLY the first element listed in the chemical formula OR look for least EN

exceptions:

- diatomic compounds (2 atoms)

-Hydrogen is the starting element

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Single dots (lone e-) on a Lewis structure show…

Bonding sites & if you count them up the ideal # of bonds

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Can you reduce the formula of a covalent compound

NO, NEVER.

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Formal charge equation

FC= VE-CB-NE

The # of valence electrons (from periodic table) - # of covalent bonds on the atom (on the LS) - # of non-bonded e- (on the LS)

-Do this for each atom in the compound and then add up their charges to see the compounds overall charge

-Most stable is zero UNLESS it’s a polyatomic in which case it would be the charge of the polyatomic that is most stable

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Polyatomic ions

Polyatomic’s have both ionic and covalent character (covalently bonded cluster of atoms with an ionic charge)

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How to show polyatomic ions lewis structure

Put the compound in parentheses and put the charge on it’s upper right corner

<p>Put the compound in parentheses and put the charge on it’s upper right corner </p>
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Things that have multiple bonds are more ___ than single bonds

Conductive

this is bc the transfer of e- is quicker & more efficient

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Resonance structures

Resonance structures show the multiple ways bonding can occur in a compound

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Why are resonance structures caused

They are caused when there is more than one way to place double bonds and lone pairs on atoms

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Coordinate bond

When both bonding e- are donated by a single atom

ie. this happens when one atom is satisfied and another isn’t, the satisfied atom will share 2 of it’s e with the other atom, forming a bond, to satisfy it so the whole compound can be more stable

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Multiple bonding

Double or Triple bonds

-these occur to satisfy atoms that do not fulfill the octet rule

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Why are excess atoms theorized to happen

The D sub-level acts like a trunk where extra e- can be stored if need be, this is why we can fit 10 e- on some atoms instead of only eight, bc 2 would be in the “trunk”

The bonds are SPD hybrids when this happens

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How many e- can Sulfur hold?

12*

*only when acting as a central atom!

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How many e- can Phosphorus hold?

10*

*only when acting as a central atom!

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How many e- can Hydrogen hold?

2

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How many e- can Boron hold?

6*

*only when acting as a central atom!

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How many e- can Beryllium hold?

4*

*only when acting as a central atom!

*Note, this is a metal but it’s EN is close to NM so it can covalently bond

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What are the deficit atoms

Atoms that are stable with less than 8 e-

These are H, B, Be

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What are the excess atoms

Atoms that can hold 8+ e- but can be stable @ 8

These are P, S, Noble gases & Halogens (NG and Halogens are VERY rare)

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Why are covalent bonds NOT conductive

Bc they do not have charged particles capable of transporting e-

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Melting and boiling point increases with…

Molar mass

more mass= more substance to melt

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State of matter @ room temp for covalent bonds

Can be solid, liquid, or gas

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Why do covalent bonds have low MP/BP

Bc they have weak forces of attraction btwn them. Since covalent bonds form btwn NM’s there is no opposite charges & therefore no coulombic attraction, this makes the force weaker. The e- are also shared, not transferred, making a weaker bond which is easier to break and therefore a lower MP/BP

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Properties of covalent bonds

-low melting/boiling point

-soluble (dissociates in water)

-non-conductive

-share e- to achieve octet

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How does e- sharing work

Covalent bonds share e- via. orbital overlap

-more overlap (ie. double & triple bonding) = stonger bond

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Covalent bonds occur so that…

They can act like noble gases (and be stable)

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What is the rep. particle name for covalently bonded atoms

Molecule

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Covalent bonds are formed btwn…

Non-metals only*

They share electrons

*Some metalloids bond with nonmetals and tend to form covalent bonds

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Lone pair/unshared pair

pair of e- that are NOT shared btwn atoms

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Where does hybridization occur

ONLY on the central atom