Biology Chapter 2

How many orbitals are in the second energy level?

2 - 1s and 3p orbitals. The s holds 2, the p holds 6, so 8 electrons overall.

How many orbitals are in the third energy level?

3 - 1s, 3p, 5d. the s holds 2, the p holds 6, the d holds 10. Therefore there are 18 possible electrons in the third shell

Which of the following four statements, if any, is true regarding essential elements and living organisms? -the elements carbon, hydrogen, nitrogen, and oxygen make up 20-25% of living mass. -All organisms require 25 of the 92 naturally occurring elements to survive. -Given their low concentrations in nature, the toxicity of some elements is generally not a factor in the evolution of biological communities. -Although all forms of life require iron, other elements are required only by certain species. -All of the listed responses are correct.

Although all forms of life require iron, other elements are required only by certain species.

All chemical reaction are interactions between what of an atom?

Electrons

Where is an electron's potential energy highest?

Electrons hare attracted to the nucleus. the farther away from the nucleus, the more work will be needed to put into the system to move a given electron farther away, and the more potential energy.

What happens when an electron abosrvs energy? Loses energy?

Electrons that absorb energy (endothermic reactions) move to a shell away from nucleus. When it loses energy (exothermic reactions), it falls back to a shell closer to the nucleus. The lost energy is heat out to the environment.

What is an element?

Element is the smallest substance of matter. It can not be broken down into other elements in a chemical reaction.

Evaluate the following statement: Concentrations of trace elements in an environment above what is required by organisms generally has no effect on those organisms. -False. Elevated concentrations of trace elements such as chromium and phosphorus can be toxic. -True. Only trace element limitation can lead to disease among organisms. -False. Increasing the concentration of trace elements above what is required generally has a beneficial effect on organisms. -False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic. -True. Most organisms have evolved adaptations that allow them to tolerate very high concentrations of trace elements in the environment.

False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.

What is electronegativity?

It is the tendency to pull electrons to itself. Electronegativity depends:1) on how many electrons are missing (just missing 1, most electronegative like flourine, will pull very hard to get 1 more electron) as well as 2) size (large atom is, less electronegative because other electrons shield the nucleus from trying to pull outside electrons into its web.

Do compounds have the same properties as their elements?

No

Are atoms the first characteristic of life?

No because living and non living things are made up of atoms. Molecules are the first characteristics of life because macromolecules are found only in living things (emergent property).

Model of an atom

Notice that the denser the shading, the more dense the electrons are. Bulk of mass is in the nucleus.

What is the mass of aproton and neutron? An electron?

Proton and Neutrons are 1.7 x 10^-24 kg. An electron is about 1/2000 of an amu.

What is the atomic mass?

Protons + Neutrons; will tell you what the mass of that is in a mole. This is in superscript when written to th eleft.

Consider a hypothetical atom with an atomic number of 4 and a net electronic charge of +1. How many neutrons does this atom have? -one -three -four -The answer cannot be determined from the information provided. -None of the listed responses is correct.

The answer cannot be determined from the information provided.

What are are hydrogen's three isotopes?

deuterium (1 neutron), tritium (2 neutrons)

Chemical reactions

make and break chemical bonds. Turns reactants into products.

Chemical equilibrium is

when the rate of the forward and reverse reactions are the same and the relative concentration sof product/reactans stop changing. The ratio is now fixed. Does not mean that reactants and product are in equal amounts.

what are the four most important elements tha tmake up 96% of life?

Carbon, Oxygen, Hydrogen and Nitrogen

What is a positive ion called? A negative one?

Cation (+), Anion (-)

Discuss what determines the chemical behavior of an element and why the atoms of some elements have more of a tendency to react chemically than others.

Chemical reactions are all interactions between atom's valence electrons. The extent of an atom's reactivity is based on the number of valence electrons it has. For example, atoms with filled valence shells are not reactive at all, while atoms that only need one electron to fill their valence shell (the halogens) are highly electronegative and reactive. Additionally, atoms that only have one or two in their valence shell tend to want to lose those atoms in order to become a complete octet; hence why the would react with atoms that are in need of electrons by giving up their electrons. Metals in group 1 and group 2 will give up their extra electrons and will become ions. Usually the partner atom will be atoms in group 6 or 7 that will gladly accept the ion and will therefore become an anion.

What is a compound?

Compounds are made up of 2 or more elements.

What is the rate of reaction dependent on?

Concentration of reactants Presence of catalysts temperature

chemical properties are determined by

Distribution of electrons in atom's valence shell. Atom with completed balence shell is unreactive. Elements with the same group have similar poroperties. If an element is in the first two groups, they only have one or two extra. They tend to give them up so they can have a full 8 in their valence shell. Elements in 7 and 8 (halogens) tend to pull 1 or 2 in order to complete their 8. they make ionic bonds.

What is a non polar covalent bond?

Equal sharing. These are hydrophobic.

What is a hydrogen bond?

Hydorgen bonding is when a hydrogen atom that is covalently bonded to one electronegative atom is also attracted to another electronegative atom. these are transient!!! And always involve hydrogen!!! and also H,F,O,N,S.

What are two weak chemical bonds?

Hydrogen bonding Van der waal's forces

What is the atomic number?

Identifying number of an element. It tells the number of protons. This is in subscript when written to the left.

What is polar covalent in terms of electronegativity?

If the difference is .5 to .8

What are the three atomic particles of an atom and what are its charges? Where are they located?

In the nucleus - proton (+) and neutron (0). Swimming around the nucleus in orbitals, electrons (-).

what compounds do ionic bonds form?

Ionic bonds form cyrstals called salts. They harden into three dimensional lattices.

what is an isotope?

Isotopes are different atomic forms of an element that have different number of neutrons, therefore different masses. Isotopes can be stable or radioactive.

What is a polar covalent bond?

One or more electronegative atoms are more electronegative than others, and are bonded. This causes partially positive/negative poles, hence "polar" molecules. They are hydrophilic and dissolve in water.

How many orbitals are in the first shell?

1s orbital, which holds 2 electrons

How many naturally occuring elements are there?

There are 92 (up to Uranium). Everything afterwards is man made.

what is an ionic bond?

Two atoms are so unequal, their attraction for the valence electron causes the most electronegative atom to trip the atom completely away. Ions have net charge.

A hydrogen bond is a

Weak chemical bond.

Under what circumstances do two atoms for an ionic bond?

When one is a metal and has an extra one or two electrons that it wants to lose and another one is missing one or two and is a non metal (probably a halogen) that wants to gain electrons. These two would bond via ionic bonding.

Mass - protons equals

electrons

What is a chemical bond?

interactions that result in atoms staying close together.

What is a covalent bond

strong, sharing of a pair of valence electrons by two atoms. Can be single, double, triple.

In hydrogen bonds, its important to note that

the two molecules must be polar the two molecules are already participating in covalent bonds with other molecules they are transient

Model of energy levels

• In order for electron to move outside, it must absorb energy (endothermic) • In order for electron to move in, it gives up energy (exothermic) The closer the electron is to the nucleus, the stronger the attraction to the nucleus. Therefore, it is more difficult to escape atom