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Biology > 2.1-2.9 > Flashcards

2.1-2.9 Flashcards

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1
Q

Define matter

A

anything that occupies space and has mass.

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2
Q

Define element

A

a substance that cannot be broken down to other substances (by ordinary chemical means)

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3
Q

How many elements?

A

92

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4
Q

Define compound

A

a substance consisting of two or more different elements combined in a fixed ratio. Much more common than elements on their own in nature.

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5
Q

How is a compound an emergent property?

A

a compound has characteristics different from those of its elements. Ex. table salt. NaCl - sodium is a metal, chlorine a poisonous gas.

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6
Q

How many elements do most compounds have.

A

3 or 4

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7
Q

What makes up 96% of matter in biomass?

A

oxygen, carbon, hydrogen, nitrogen.

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8
Q

How many elements do humans need to live? Plants?

A

25, 17.

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9
Q

Besides the four most important elements, what else do humans use (4%)

A

calcium and phosphorus (bone formation) potassium, sodium, calcium, chlorine (nerve signaling). Magnesium, too.

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10
Q

Define trace element.

A

essential for humans, but in very small quantities. Ex. iron, 0.004% of body weight; needed for energy processing and transporting oxygen into blood. Iodine helps with making backbone.

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11
Q

What is commonly added to water?

A

Iodine – and other trace elements.

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12
Q

What is the disease that iodine deficiency is called, and what measures have been done to prevent it? Are they successful.

A

Goiter. Ionizing salt. over 2 billion people suffer from goiter.

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13
Q

What does fluoride help with?

A

tooth decay.

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14
Q

Define atom

A

smallest unit of matter that retains all the properties of an element.

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15
Q

What does an accurate model of an atom look like.

A

a cloud from fast-moving electrons: an incredible distance between nucleus and electron.

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16
Q

Define atomic number.

A

number of protons an element has.

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17
Q

Define mass number.

A

sum of protons and neutrons. Electrons not counted. Neutron amount not definite.

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18
Q

atomic mass

A

includes electrons. basically the same as mass number.

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19
Q

What can elements differ in? (it affects the mass number)

A

amount of neutrons. This is called an isotope.

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20
Q

How do you write isotopes?

A

element-mass number. ex. Carbon-12, carbon-13, carbon-14. (12 most common)

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21
Q

Define radioactive isotope

A

atom in which the nucleus decays spontaneously, giving off particles and energy. Harmful to organisms. Can be helpful for dating fossils.

22
Q

a nitrogen atom has 7 protons, and its most common isotope has 7 neutrons. A radioactive isotope of nitrogen has 9 neutrons. What is the atomic number of this radioactive nitrogen?

A

atomic number=7; mass number=16.

23
Q

Can organisms tell if an isotope are radioactive?

A

No, causing them to kill themselves at time. However, humans have technology to detect whether or not something is radioactive.

24
Q

How was a radioactive isotope helpful in the discovery of chemical processes?

A

By making CO2 with carbon-14 (radioactive), and letting it undergo photosynthesis, scientists were able to discover the complexities of that chemical process.

25
Q

How are radioactive isotopes helpful with diagnosis and treatment?

A

Doctors can mark questionable areas with an isotope. In addition, Alzheimer’s incorporates PIB, a radioactive isotope, which has helped them identify it early and start to create medication to fight it.

26
Q

What makes the isotopes dangerous?

A

radiation can increase thyroid cancer (where radioactive isotopes are produced), after nuclear disasters. There are natural sources of radiation too, such as radon gas and uranium.

27
Q

How many electrons can the first 3 electron shells hold?

A

2, 8, 8

28
Q

What is the outermost shell called? What does it determine?

A

the valence shell. It determines the chemical activity of the atom, as they want to fill their shells.

29
Q

How many electrons can an orbital hold? What makes an orbital and a shell different.

A

2; A shell is characterized by is circular nature, whereas orbitals are general areas where the electrons move at incredible speeds.

30
Q

What chemicals are inert (inactive)

A

the noble gases: neon and argon. Full outer shells.

31
Q

What are chemical bonds?

A

formed by trying to fill the out shell.

32
Q

How many electrons and electron shells does a sodium atom have? How many electrons are in its valence shell.

A

11 electrons; 3 electron shells; 1 electron in outer shell.

33
Q

What comprises a covalent bond?

A

when molecules share an electron.

34
Q

What does a covalent bond make?

A

molecule. Ex H2 (hydrogen gas, one valence electron each, two needed to complete)

35
Q

Examples of a single covalent bond and a double covalent bond?

A

H2: one pair of electrons shared
O2: two pairs (4 electrons) shared.

36
Q

define electronegativity

A

an atom’s attraction for shared (covalent) electrons. The more electronegative an atom, the more strongly it pulls electrons towards its nucleus.Oxygen is one of the most electronegative of the element.

37
Q

define nonpolar covalent bond.

A

where the two covalently-bonded atoms exert an equal pull on the electrons/electrons are shared equally. Examples of these bonding include H2 and O2, as they share the exact same electronegativity, and methane CH4, because the electronegativity of carbon and hydrogen do not differ much.

38
Q

Define polar covalent bond.

A

an unequal sharing of electrons in a covalent bond. The atom with the higher electronegativity pulls stronger and is therefore more negatively-charged, and the other atom(s) are more positively charged because they have less electronegativity. Example: H2O. Oxygen is more negatively charged where hydrogen is more positively charged.

39
Q

What happens when electronegativity differs by a great degree?

A

ionic bonds can be formed.

40
Q

What is chemically nonsensical about this equation: H–C= C–H

A

each C has only three bonds instead of the four required by its valence. (equation is a double bond)

41
Q

An ionic bond includes

A

the transfer of electrons, with the same ratio.

42
Q

Describe NaCl as an example of an ionic bond

A

Sodium, Na, has 11 electrons, and therefore 1 valence electron. Chlorine, Cl has 17 electrons, and therefore seven valence electrons. When sodium donates an electron to Chlorine, Sodium has a full two shells and Chlorine has a full three. However, this process makes them ions, with chlorine having a charge of 1- after gaining an electron and sodium having a charge of 1+ after losing one.

43
Q

In chemistry, how are negative ions usually written

A

with -ide at the end. The Cl in NaCl is called chloride, as it is negatively charged.

44
Q

How does the environment affect the strength of ionic bonds, using the salt example.

A

When salt is dry, and crystalized, it is very hard to break. However, it dissolves easily in water. This is how many drugs work.

45
Q

What holds together the ions in a crystal of table salt (NaCl?)

A

Opposite charges attract. The positively charged sodium ions (Na+), and the negatively charged chloride (Cl-) are held together by ionic bonds, attractions between oppositely charged ions. NaCl’s charge is neutral.

46
Q

Which bond is stronger ionic or covalent?

A

Covalent, as they form of most of a cells molecules, but weak bonds are still crucial.

47
Q

What is one of the most important types of weak bonds?

A

hydrogen bond in water.

48
Q

What behaviors of hydrogen molecules within water are allowed because of the atom’s polarity?

A

“flirting,” or because the hydrogen atoms within water are more positively charged (going back to electronegativity) they have the ability to attract the negatively charged oxygen of other water particles. One single water molecule, as described by the diagram on pg. 25, can attract up to four other molecules to weakly bond them together.

49
Q

Define chemical reaction

A

breaking existing chemical bonds and forming new ones.

50
Q

What are the parts of a chemical reaction, and what must be necessary about them?

A

Reactants –> products. There must be the same amount on each side. Take the chemical reaction: 2H2 + O2 –> 2H2O. (4 H atoms and 2 oxygen atoms). This is an explosive reaction.

51
Q

what is another famous chemical reaction necessary for sustaining life on earth?

A

6CO2+6H2O–>C6H12O6+6O2 (18 O, 6 C, 12 H). This is photosynthesis!

52
Q

Do you remember how to solve for values in chemical equations?

A

I sure hope so.

Biology (17 decks)

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