Quiz 2 - Biology (Chemical bonds.. Chapter 4)

ionic vs covalent bonds, hydrogen bonds, electronegativity, electron, chemical reactions

Recall… what’s the mass number of a lithium atom with 3 protons and 4 neutrons?

7

recall… what is true about all anions?

atom has more electrons than protons

recall.. why would an atom have no electric charge?

protons = electrons

What does the electron distribution diagram look like?

Nucleus + valence shells and the electrons

What does potential energy mean?

the energy that matter possesses because of its location or

structure, due to their distance from the nucleus

***electrons have it

what are electron shells

different “rings” (not acc in rings) that electrons go to

• they have varying average distance (from the nucleus) and potential energy level

What does the period ic portray?

the electron distribution of each element

What happens to electron # going from left to right a periodic table?

add one

What happens to electron SHELL # going from up to down a periodic table?

add one

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going to the right on a periodic table = add an electron = add one more electron to the shell

What are Valence Electrons?

electrons on the outermost shells

What are valence shells?

the outermost shells

The chemical behavior of an atom is mostly determined by…

*# of valence electrons

• Full shell = no need for more valence electrons = inert/chill atom

• Not full shell = needs valence electrons = UNSTABLE wants more/less to have a full valence

How many electrons can the 1st shell have?

2 electrons

How many electrons can the 2nd shell (and up) have?

8 electrons

What is the UN-simplified way of electron shells

orbitals

• 2 electrons per orbital

What is an orbital?

the 3 dimensional space where a electron is 90% in

How many electrons does fluorine have? How many electron shells? How many electrons are needed to complete the valence shell?

has = 9

shells # = 2

needs how many electrons to complete valence shell = 1

only ___ are directly involved in chemical reations

electrons

**Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms

what are chemical bonds?

the result of atoms interacting and staying close to each other

**hold attractions

what are the different types of chemical bonds? (2 main)

ionic and covalent

Ionic bonds do what with electrons and make the atoms into what?

atoms in ionic bonds YOINK electrons from each other

• thievery :3

• makes atoms into ions

  • Cation (pos)

  • anion (neg)

Compounds formed by ionic bonds are called what?

ionic compounds OR SALTS/CRYSTALS

ex: NaCl (sodium Chloride) = table salt

** salts = stable when dry but can dissociate/break easy when with water

The formula for an ionic compound indicates the ____ of ___ in a crystal of the salt

ratio : elements

covalent bonds

share the valence electrons - with 2 atoms

** the shared electron = part of each atom’s valence shell

what is a molecule

atoms held together by a COVALENT BOND

single bond vs doubles bond vs triple bond

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amount of electron pairs that are shared

what is a structural formula?

the notation to represent atoms and bonding

An example of the molecular formula

Abreviated form of structural formula

EX: H-H equals ….. H₂

What diagram displays Electron sharing with dots that represent valence electrons

the Lewis Dot Structure

What is an atom’s bonding capacity called?

VALENCE

Each atom that can share ___ ____ has a ___ ___ corresponding to the number of ____ ___ the atom can form

valence electrons : bonding capacity : covalent bonds

molecule vs compound

• molecule - same element OR different

  • USUALLY FOR COVALENT BONDED atoms

• Compound - two or more just DIFFERENT elements

** All compounds are molecules, but not all molecules are compounds

The Possible Number of __ __ Depends on

the Number of Missing __ __

Covalent bonds : Valence electrons

What is electronegativity?

an atom’s attraction for electrons in a covalent bond

• more electronegative an atom = stronger pull on shared electrons towards itself

***atoms in a molecule attract electrons in varying degrees

Electronegativity increases in what direction in the periodic table

• Down to up - less shells = electrons are less far from the nucleus

• Left to right = more electrons are added - atomic radius decreases

non polar vs polar covalent bonds

• NON - electrons shared equally

• POLAR - electrons not shared equally + one atom is more electronegative → causes a partial positive or negative charge for each atom or molecule

  • EX: H20

usually the strongest bonds are …

covalent bonds - helps form cell’s molecules

weak bond/”interaction” contribute greatly to what?

• the emergent properties of life

  • reversable → 2 molecules affect each other briefly and then separate

** many larged biological molecules are held int heir functional form by these week interactions (… carbs and lipids??)

Example of a weak bonds/interaction

• hydrogen bonds

What are Hydrogen Bonds?

• when hydrogen atoms are covalently bonded to a electronegative atom AND is also attracted to another electronegative atom

  • Basically a guy is in a healthy relationship but decides to “eye” up another girl

• in living cells .. it’s usually oxygen or nitrogen

What are Van der Waals interactions?

Dipole - creates a negative side and a pos side… and influences another molecule to do the same

• they turn until on pos side and one neg side get attracted to each other

• like a bipolar girl… transforming her friend into a bipolar guy and then getting attracted to each other getting attracted to each other

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attractions between molecules that are close together as a result of molecule with electrons that weren’t evenly distributed

• accumulated in 1 side

Molecular size and shape are key to its ______

function

• Shape - if complimentary, 2 molecules can bind temporarily

  • Ex: Opiates (morphine/ natural endorphins) have similar shapes, receptors, and effects/functions

molecular shape is determined by __________

• its atom orbital positions

what happens when atom forms covalent bonds?

• the orbitals in its valence shells get rearrange

What shape does a orbital shape look like when both s and p orbitals are filled?

• four new hybrid orbitals shaped like identical teardrops extending from the atomic nucleus (like one of Ms. veronica’s balloon structures before its added to the big rainbow)

Molecules like methane (CH4) … has what shape?

• TETRAHEDRON

• share all four of their hybrid orbitals with another atom

Molecules like water has what shape?

• a “V” - 2 covalent bonds at an angle of 104.5 degrees

  • H20 = lone pairs of electrons on the oxygen atom occupies 2 of the hybrid orbitals

Chemical reactions… ___ or ___ bonds

make : break

• results in composition of matter to change

Parts of a chemical reaction

• reactants - starting molecules (on the left side)

• products - resulting molecules (on the right side)

• Coefficients - number of molecules (not elements)

What is another way of saying “Matter is conserved in a chemical reaction“

Reactions cannot create or destroy atoms but can only rearrange (redistribute) them

• All atoms of the reactants must be accounted for in the products

All chemical reactions are theoretically….

reversable : two opposite headed arrows indicate a reaction is reversable

The concentration of the ____ impacts the rate of ____ ___

reactants : chemical reactions

**higher concentration = more frequently do the molecules collide with each other → more chance to react and form products

How is chemical equilibrium reached?

when the forward and reverse reactions happen simultaneously

• the concentrations of reactants and products don’t change

Check understanding : The reactivity of an atom arises from…

(A) the average distance of the outermost electron shell from the nucleus.

(B) the existence of unpaired electrons in the valence shell.

(C) the sum of the potential energies of all the electron shells.

(D) the potential energy of the valence shell.

B → the existence of unpaired electrons in the valence shell

• full = not reactive

• not full = reactive

• they want to take/remove electrons to become stable :)))

Not a → it’s for electronegativity (how strong an attraction is has) not how reactive it is → EX: noble gases (great distance from nucleus BUT not reactive.. cause it’s full)

not c → the total sum of the potential energies across all electron shells dictates the overall electronic structural stability of the atom, rather than its specific inclination to participate in external chemical interactions

not d - while the potential energy of a valence shell is a distinct property based on its distance from the nucleus, static potential energy alone does not force an atom to react. A full valence shell still contains high potential energy but results in an inert, non-reactive element

Check understanding :

An atom of oxygen has an atomic number of 8. How

many electrons are in the first, second, and third

electron shells, respectively?

(A) 2, 3, 3

(B) 2, 6, 0

(C) 8, 0, 0

(D) 0, 4, 4

(E) none of the above

B → 1st shell only carries 2 , the rest carry 8! (in other words its valence shell is not full… it’s reactive)

Check understanding:

Which of the following statements correctly describes

any chemical reaction that has reached equilibrium?

(A) The concentrations of products and reactants are equal.

(B) The reaction is now irreversible.

(C) Both forward and reverse reactions have halted.

(D) The rates of the forward and reverse reactions are equal.

D!

NOT A → just because they are in equilibrium doesn’t mean their CONCENTRATION (how much per stuff) is the same

• their concentration is CONSTANT/unchanged, but not equal (in #)

  • Ex: more products are made than reactants provided (vise versa)