Chapter 2 bio- elements atoms and bonds
Hydrogen bonds occur when __________.
partially opposite charged molecules come close enough to attract each other
electron orbital
- An electron orbital describes a three-dimensional space where an electron can be found 90% of the time. -these orbitals are the 1s,2s,2px,2py,2pz we cannnot know the exact location of an electron. Instead, we can describe a three-dimensional space in which an electron spends most of its time.
what are some of the application of isotopes today?
-Dating fossils -diagnosing medical disorders - -tracing atoms through metabolic processes
Are chemical reactions reversible?
all chemical reactions are reversible - -the products of the forward reaction become the reactances of the reverse reaction
electronegativity
an atoms attraction for the electrons in a covalent bond -the more electronegative an atom the more strongly it pulls shared electrons to itself
isotopes
atoms of a SAME ELEMENT that have the same number of protons but may differ in the number of neutrons ( resulting in different charges ) -- -most isotopes are stable but some are radioactive, giving off particles and energy -
Hydrogen bonding is most often seen _____. a. when the bonds within the molecule are nonpolar covalent bonds b. if the molecule consists of three or fewer atoms c.when hydrogen is covalently bonded to an electronegative atom d. when multiple carbon atoms are present in molecules whose three-dimensional shape is tetrahedral
c. Highly electronegative atoms attract shared electrons more strongly than hydrogen does, resulting in a slight positive charge on the hydrogen atom. The slightly positive hydrogen atom is then attracted to another electronegative atom, forming a hydrogen bond.
*hydrogen bonds
forms when a hydrogen atom covalently bonded to one electonective atom and is also attracted to another electronegative atom - in living cells the electronegative partners are usually oxygen or nitrogen atoms -This attraction is called hydrogen bonding. Ionic and covalent bonds are INTRAMOLECULAR bonds, meaning that they exist inside the molecule. These bonds deal with the exchange of electrons. Hydrogen bonds are INTERMOLECULAR bonds, meaning they bond two separate molecules. Just remember covalent bonds are the sharing of electrons whereas hydrogen are the bonds formed between hydrogen and a highly electronegative atom.
Chemical equilibrium
is reached when forward and reverse reactions rates are equal -ex photosynthesis - sunlight powers the conversion of carbon dioxide and water to glucose and oxygen - the reactions blushes back and forth at equal rates creating an equilibrium
atomic number
represents the number of PROTONS in the element -this is the smaller number on the periodic table symbols -this will be true regardless of the charge of the atom, if you change the number of protons in the atom you change the type of elemental atom
Chemical reactions -reactants -products
- the making and breaking of chemical bonds -the starting molecules of the chem reactions -the resulting molecules of the chemical reactions
Valence shell descriptions
1st shell = 1s = can hold 2 electrons 2nd shell (holds 8 electrons total ) and has four orbitals -2s - holds 2 electrons -2px- holds 2 electrons -2py - holds 2 electrons -2pz - holds 2 electrons These all form the 2nd shell but work in a three dimensional orbit , like a sphere
What are the three types of bonds
Covalent - sharing of pairs of electrons - polar covalent - non polar covalent Ionic - Hydrogen
hydrogen bonds note card 4
Hydrogen bonds occur when partial opposite charges on molecules come close enough to attract each other Hydrogen bonds are NONCOVALENT bonds that result from an attraction between a hydrogen molecule that is already covalently bonded to an electronegative atom, and another electronegative atom. **Hydrogen bonds thus form between molecules with partial opposite charges**
anion facts
The atom has more electrons than protons is true of all atoms that are anions. This is a definition question. Remember that protons carry a +1 charge, electrons carry a -1 charge, and neutrons carry no charge. An anion is an atom that has more electrons than protons and carries a negative charge. Anions DO NOT always have negative charges of -1: the number of electrons can exceed the number of protons by more than 1. An atom with fewer protons than the neutral atom of the same element would be a different element. Having more neutrons than protons would not affect the charge on the atom.
Which statement is true of all atoms that are anions?
The atom has more electrons than protons. Anion - Gains an electron and become more -negative
what creates a neutral atom ?
The number of protons is equal to the number of electrons.
covalent bond
The sharing of pairs of electrons in a molecular bond. Remember this is the sharing of pairs of electrons. so the sharing of 4 electrons would be the sharing of two pairs of electrons.
cation (+)
a positively charged ion -- >lost an electron -has more protons than electrons A cation is an atom that has more protons than electrons and carries a positive charge (think of the "t" in "cation": it looks like a "+" sign).
radioactive
an unstable element or product that can spontaneously decay
Ionic compound
compounds formed by ionic bonds are called ionic compounds or salts
Nonpolar covalent bonds are always formed from atoms that are __________.
equal in their electronegativity. The definition of a 'non polar covalent bond' is the EQUAL sharing of electrons in the covalent bond.
non polar covalent bonds
equal sharing of electrons -bonds between atoms with similar electronegativitys
In a process called radiometric dating, scientists measure the __________ of an isotope to determine the age of the Earth.
half life
What are the four most abundant elements found in living systems?
hydrogen oxygen nitrogen carbon
anion
negatively charged ion --> gained an electron -has more electrons than protons
element
per the homework - a substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) - this is the same definition of an atom -each element has its own unique atoms so this definition may be interchangable
atoms
smallest functional units of matter that form all chemical substances -cannot be further broken down by ordinary chemical or physical means -each element has its own unique atoms
half-life
the time it takes for 50% of the parent isotope to decay - or the time it takes for 50% of radioactive atoms to decay
Daltons
the unit used to measure protons/ neutrons --> sub - atomic particles and their charges protons +1 neutrons 0 electrons -1
atomic mass
total mass and will have decimals points , total mass of the protons + neutrons This will be the larger number on the periodic table
Ionic bond part 2
transfer of an electron from one atom to another results in a positive ion (cation) and a negative ion (anion), which usually attract each other to form an ionic bond. However, the ions need not have acquired their electrical charge due to an electron transfer with each other.
In ionic interactions, the transfer of valence electrons results in a completed valence shell for each ion true or false
true
polar covalent bonds
unequal sharing of electrons -this results in a partial negative region and a partial positive region in the molecule -p covalent bonds occur because the distribution of electrons around the atoms create polarity, or difference in electric charge across the molecule causing it to attract to other atoms -water is a classic example of polar covalent bonds H2o
Trace Elements
Trace elements are required by an organism in minute quantities. -small amounts of elements that are needed by organisms to survive Some trace elements, such as iron (Fe), are needed by all forms of life; others are required only by certain species.
true or false : Although all forms of life require iron, other elements are required only by certain species.
True :species differ in the number of essential elements they require: Humans need 25, but plants require only 17. Carbon, hydrogen, nitrogen, and oxygen make up a large proportion—about 96 percent—of living matter. All forms of life require iron, whereas other elements are needed by certain species only; for example, humans and vertebrates need iodine, but invertebrates do not. Toxic elements can play an important role in evolution, as in the case of the plants that have adapted to survive in serpentine soil, which has high levels of toxic elements like chromium, nickel, and cobalt. these are examples of trace elements
ion
a charged atom, positive or negative -Atoms with the same number of protons but with different electrical charges
The atoms of different phosphorus isotopes _____. a. have a different number of neutrons b. have the same number of electrons c. have a different number of protons d. have electrons equal to neutrons
a. have a different number of neutrons the phosphorus atom is defined by its proton number -Changes in neutron number does alter the mass of the atom, but DOES NOT change its chemical behavior or reactivity. -Chemical behavior is dependent on the electrons in the shells
If a covalent bond is sharing the total of 4 electrons what is the correct description of that molecular bond?
double covalent - Remember * covalent bonds are the sharing of PAIRS of electrons -The atoms are sharing two pairs of electrons. will show a graphic of four total electrons being shared
Compared with 31P, the radioactive isotope 32P has______ (P is phosphorous with an atomic number of 15)
one more neutron -the number of protons in an atom is what makes it that specific element -the atomic mass is made of the protons + neutrons. If the number of neutrons is different ( forming an isotope of that same element) the atomic mass can increase while still having the same number of protons AKA being the same element with different atomic masses.
Hydrogen bonds note card 3 Weak chemical bonds such as hydrogen bonds __________.
when a hydrogen atom that is a covalently bonded to an electronegative atom like oxygen or nitrogen is attracted to another electronegative atom
Which of the following is a trace element required by most living organisms? -oxygen -nitrogen -carbon -magnesium -hydrogen
By weight, magnesium accounts for only 0.1% of most living things.
hydrogen bonds note card
Hydrogen bonds occur when partial opposite charges on molecules come close enough to attract each other. Hydrogen bonds are NONCOVALENT bonds that result from an attraction between a hydrogen molecule that is already covalently bonded to an electronegative atom, and another electronegative atom. Hydrogen bonds thus form between molecules with partial opposite charges. Electrons are shared in covalent bonds, but NOT in hydrogen bonds.
ionic interactions note card - good card
In ionic interactions, the transfer of valence electrons results in a FULLY COMPLETED VALENCE shell for each ion. When two atoms are very unequal in their attraction for valence electrons, the more electronegative atom strips an electron completely away from its partner. The two resulting oppositely charged atoms (or molecules) are called ions. A positively charged ion is called a cation, while a negatively charged ion is called an anion. Because of their opposite charges, cations and anions attract each other; this attraction is called an ionic bond. *Note that the transfer of an electron is not, by itself, the formation of a bond; rather, it allows a bond to form because it results in two ions of opposite charge.* Any two ions of opposite charge can form an ionic bond. *The ions do not need to have acquired their charge by an electron transfer with each other.*
Changing the number of _____ would change an atom into an atom of a different element.
Protons - Atoms of each element have a unique number of protons within their nuclei. Changing the number of protons in an atom occurs only in nuclear reactions, not chemical reactions. -this only applies to protons if one was the change the number of the neutrons it would only change the isotope of the same element not the element itself
proton, neutron and electron masses
The proton and neutron both have masses of about 1 amu, whereas the electron mass is only about 5.5×10−4amu. -point - electrons are much smaller in regards to mass relative to protons and neutrons which are of equal mass
Which statement about weak bonds is correct? a -Weak chemical bonds form only between atoms of similar electronegativity. b -Weak bonds are less important to living things than strong covalent bonds. c - Weak bonds are transient and easily reversible.
c. Molecules that form weak bonds can come together, interact, and then separate. The combined effect of many weak and transient hydrogen bonds or Van der Waals interactions can produce important emergent properties. Read about the importance of the transience of weak bonds such as hydrogen bonds, ionic bonds, and Van der Waals interactions.
Van der waals interactions
molecules or atoms that are very close together can be attracted by fleeting charge differences if electrons are distributed asymmetrically in molecules in atoms -these are weak attractions between molecules that are close together as a result of the charge -Weakest of attractions/ bonds - they have a very short term lived attraction
energy
the capacity to cause change
ionic bond
the complete stripping or transfer of electrons - this is also known as the attraction between an anion and a cation -an attraction between ions of opposite charge -leaving the atoms both charged -cation and anion -salt (NaCl) is an example of an ionic bond -Na has 11 atomic number and Cl has a 17 Atomic number , these are a perfect fit to transfer 1 electron from Na to Cl to fill its outer valence shell
potential energy
the energy that matter has because of its location or structure -electrons in the valence shells of an atom have potential energy. -the further shell the electron is on the more potential energy it has
molecular shape
the molecular shape is determined by the positions of its atoms valence orbitals and is very important to its functionality - every molecule has a specific share formed by its bonds and atoms -this is how synthetic medicines are created - by creating similar molecular shapes to fit into proteins or other molecules - ex morphine molecule is shaped the same as a natural endorphins to create that same type of feeling/stimulus
What determines the types of chemical reactions that an atom participates in?
the number of electrons in the outermost electron shell