sem - 1 Flashcards
1
Q
Who created the 1st periodic table & when?
A
- Dmitri Mendeleev published the 1st periodic table in 1869
2
Q
How was Dmitri Mendeleev’s periodic table organized?
A
- organized in order of increasing atomic mass
- the new version of the P.T arranges the elements based on increasing atomic number
3
Q
What similarities do elements within a group show?
A
- similar chemical properties & reactivity b/c they have the same number of valence electrons
4
Q
Differentiate between metals & nonmetals.
A
- metals are great conductors of heat & electricity where as nonmetals are poor conductors of the two
5
Q
Which groups on the periodic table have the most reactive elements?
A
- group 1 = alkali metals
- group 7 (VII) = halogens
6
Q
What are valence electrons and what do they do?
A
- they are the electrons on the outermost shell of an atom
- they participate in the sharing or exchanging of electrons between other atoms which is responsible for chemical rxns
7
Q
What are the 3 factors that the attraction between the positive nucleus and valence electrons depend on?
A
1- number of protons in the nucleus
2- distance from the nucleus
3- shielding effect of other e- closer to the nucleus
8
Q
What is the effective nuclear charge (Zeff)?
A
- it is the nuclear charge of an electron when both the actual nuclear charge ‘Z’ (the atomic # of the element) and the repulsive effects (shielding e-) are taken into account.
Zeff = Z (the atomic number/number of protons of the element) - S (the total number of shielding e-)
9
Q
In the Zeff = Z - S (or sigma sign) formula, the sigma is called what?
A
- it is called the shielding constant & it is greater than 0 but less than ‘Z’
10
Q
Zeff (effective nuclear charge) increases which ways on the periodic table?
A
- increases moving left to right
- increases moving down the periodic table (per slaters rule)
11
Q
What is slaters rule?
A
- his rule calculates sigma (S) by accounting for the effective shielding of e- in each orbital shell
12
Q
Define atomic radius.
A
- it is the distance between the nuclei of two combined/adjacent atoms
13
Q
How does the atomic radius vary going left to right across a period? Why?
A
- the atomic radius decreases
- because there is an increase in atomic # (Z) so there is an increase in the number of protons in the nucleus. this means there is an added e- to the same energy level and that causes Zeff to increase. There will be a bigger attraction and so the atomic radius decreases. (Think of class increasing the number of students analogy)
14
Q
How does the atomic radius vary going down a group? Why?
A
- atomic radius increases
- because more protons means more e-. The e- enter another energy level so there is now a greater distance between the nucleus and outermost shell.
15
Q
What is ionic radius?
A
- it is the radius of a cation (when an atom has more protons than e-) or an anion (when an atom has more e- than protons)
16
Q
How does the ionic radius change when we form an anion (X-)?
A
- ionic radius increases
- Cl = 17+ protons & 17- electrons
- Cl- = 17+ protons & 18- electrons
- the additional electrons cause a greater repulsion amongst the e- so size increases.
17
Q
How does the ionic radius change when we form an cation (X+)
A
- it decreases
- Na = 11+ protons & 11- electrons
- Na+ = 11+ protons & 10- electrons
- we get rid of an electron so now there are less electrons which means there is less repulsion amongst the electrons so size decreases.
18
Q
Define what isoelectronic is.
A
- it is when 2 elements have the same electron configuration (or same # of electrons)
- ex: Na+ = 11+ protons & 10- electrons
Mg +2 = 12+ protons & 10- electrons
both have electron configuration of
1s^2 , 2s^2 , 2p^6
19
Q
Is the ionic radius of a dispositive ion greater or less than the radius of a unipositive ion? Explain.
A
- ionic radius is less than the unipositive one
- This is b/c the dipositive ion has a bigger nucleur charge, therefore causing a bigger attraction so the size of the radius decreases.
- example:
Na+ = 11+ protons , 10- electrons
Mg 2+ = 12+ protons , 10 - electrons
20
Q
Is the ionic radius of a dinegetive ion larger or smaller than the radius of a uninegetive ion? Explain.
A
- dinegetive ion has radius that is larger than the radius of a uninegetive ion
- b/c there are 2 more electrons than protons so attraction is weaker (so bigger size) whereas the uninegetive ion only has 1 more electron than proton so attraction is still strong.
- example:
O -2 = 8+ protons , 10 e-
F -1 = 9+ protons, 10 e-
21
Q
We know that ions move through tiny channels in cell membranes. However, some channels allow ____ through but not larger than ____ ?
A
- allow Na+ through
- but not larger than K+
22
Q
Define ionization energy (IE)
A
- it is the minimum energy required to remove the most loosely bound electron from a gaseous atom in its ground state.
23
Q
Define and give examples of 1st VS 2nd VS 3rd ionization energies.
A
- First ionization energy (IE 1) is the removal of the first most likely bound e- from 1 mol of the gaseous atom to produce 1 mol of gaseous atom with a +1 charge
- Second ionization energy (IE 2) is the removal of the most likely bound e- from 1 mol of the gaseous ion with the +1 charge to produce a mol of gaseous ion with a +2 charge
- Third ionization energy (IE 3) is the removal of the third most likely bound election
- Examples:(IE 1) = Mg (g) —> Mg+ (g) + e-
(IE 2) = Mg+ (g) —> Mg +2 (g) + e-
(IE 3) = Mg +2 (g) —> Mg +3 (g) + e-
24
Q
How does ionization energy vary going across a period Vs down a group?
A
- increase going across a period b/c number of protons (aka nuclear charge) increases so bigger attraction to the electrons. bigger attraction means bigger ionization energy b/c more energy is needed to pull the e-
- decreases going down a group b/c there is a greater distance between the nucleus & outermost shell/electron. distance weakens attraction between the nucleus and outermost electron so less energy is required to steal that loose electron.
25
What are the exceptions to the trend in ionization energy? Why?
- [ Be and B ]
Be comes before B so it’s ionization energy should be lower but it’s actually higher.
This is because ‘Be’ Electron configuration is 1s^2 , 2s^2
whereas
‘B’ Electron configuration is 1s^2 , 2s^2 , 2p^1
The electrons in the ‘p’ orbital is further from the nucleus than electrons in the ‘s’ orbitals so they require less energy to removed
- [ N and O ]
N comes before O so it’s ionization energy should be lower but it’s actually higher.
‘N’ has an electron configuration of 1s^2 , 2s^2 , 2p^3
whereas
‘O’ electron configuration is 1s^2 , 2s^2 , 2p^4
In oxygen, the electron is removed form a doubly occupied p orbital. In that doubly occupied orbital, the 2 electrons are repelling each other and so less energy is required to remove the e- than an e- in a half-filled orbital
26
Which group had the highest and lowest ionization energies?
- Alkali Metals (group 1) - lowest ionization energy
- Nobel Gases (group 8) - highest ionization energy
27
Define electron affinity.
- is the negative change in energy that occurs when a neutral atom in gaseous state gains an e- , releasing energy in the process. This makes the atom now an anion
- the likelihood of a neutral atom to gain an e-
28
What is the difference between high Vs low electron affinity?
- high EA = atom more easily accepts electron
- low EA = atom less easily accepts electron
29
F (g) + e- —> F- (g)
Energy = -328 kJ mol^-1
So electron affinity is + 328 kJ mol^-1
Explain this.
- fluorine accepts an electron and becomes F- all the while releasing energy.
- Since releasing energy is an exothermic process, the change in energy has a negative sign which means that the electron affinity is positive.
- The more positive or the more higher the Electron affinity of an atom indicates that the atom can more easily accept an electron
30
Define electronegativity.
- it’s the ability of an atom to attract electrons towards itself while in a chemical bond.
- nonmetals tend to be electronegative (get electrons) while metals tend to be electro positive (give away electrons)
31
What is the most electronegative element? Why?
- Fluroine.
- Because it has a high electron affinity (tends to pick up e- easily), high ionization energy (does not lose electrons easily), and it has a high nuclear charge with little shielding
32
Explain the movement of dipole in H-F.
- F is more electronegative than H (can attract e- toward itself more strongly) so the movement of the e- goes towards F
————>
H - F
33
Describe the electronegativity trend on the periodic table.
- increases across a period (left to right)
- decreases going down a group
34
What is a molecule?
- two or more atoms held together via chemical forces/bonds
- can contain atoms of the same element or atoms of two or more elements
35
What is a diatomic molecule?
- a molecule that contains only 2 atoms
- ex: O2, H2, B2, Br2, HCl, CO
36
What is a polyatomic molecule?
- a molecule that contains more than 2 atoms
- ex: H2O, O3, NH3, CH4
37
What is a molecular formula?
- it shows the exact number of atoms of each element in a molecule
- ex: Glucose —> C6H12O6
C = 6 atoms
H = 12 atoms
O = 6 atoms
38
What is atomic mass?
- the mass of the atom in atomic mass units (amu)
39
1 amu (atomic mass unit) is defined as what?
- a mass equal to 1/12 the mass of one carbon-12 atom
40
Define average atomic mass.
- the average mass of all the naturally occurring isotopes of the element.
- mass x abundance %
41
Define molecular mass/weight.
- it is the sum of the atomic masses (in amu) in a molecule
- ex: SO2
1S = 32.07 amu
2O = 2 x 16 amu
—————————
SO2 = 64.07 amu
42
For any molecule
Molecular mass (amu) = molar mass (grams/mol)
1 molecule of SO2 = 64.07 amu
1 mol of SO2 = 64.07 g SO2
43
What is a chemical reaction?
- process in which a substance is changed into 1 or more new substances
44
What is Avogadro’s number?
6.022 x 10^23
45
1 mole of atoms = how many atoms?
1 mole of molecules = how many molecules?
• 6.022 x10^23 atoms
• 6.022 x10^23 molecules
46
What is molar mass?
- mass in grams of 1 mole of molecules or 1 mole of atoms
- unit for molar mass is g/mol
47
1 mole of atoms contains 6.022 x 10^23 atoms and has what kind of mass?
- atomic mass
48
1 mole of molecules contains 6.022 x 10^23 molecules and has what kind of mass?
- molecular mass
49
Difference between solute vs solvent?
- solute = substance being dissolved
- solvent = substance doing the dissolving
50
What is a solution?
- homogeneous mixtures of 2 or more substances that can be formed in any state of matter
Example:
Solute (NaCl) + Solvent (H2O) = Saline solution
51
The human body is made up of what percentage of water?
- 60%
52
The body is comprised of how many L of
a) water
b) blood plasma
c) intracellular fluid
d) extracellular fluid
a) 40 L
b) 3 L
c) 25 L
d) 12 L
53
What is a solution concentration?
- the concentration of a solution is the amount of solute present in a given amount of solvent or solution
54
Explain the difference between dilute solution and concentrated solution.
- dilute solution = contains relatively little solute in a large quantity of solution
- concentrated solution = contains relatively large amounts of solute in a given quantity of solution
55
What are the two quantitative ways to measure the concentration of a solution?
- using concentration percentage
• used in clinical reports, medicines, IV drips, etc.
- molar concentration (molarity)
56
Units of measure of water:
a) 1 ml = ? grams
b) density = ?
a) 1 gram
b) d = m/v
57
What is the Intravenous Drip (IV drip)?
- it is the giving of substances directly into a vein
58
Why would one need intravenous drip therapy?
- when they can’t swallow safely due to being under a coma or anaesthesia
- when they require medication which are destroyed by their gastric juices or are poorly absorbed by the gastrointestinal tract
- when they must rapidly increase the concentration of medication (morphine) or electrolyte
- when they can’t drink enough to keep up w/ the loss of fluids (major burns. Severe diarrhoea, haemorrhage, etc)
59
Is the I.V drip hypertonic, isotonic, or hypotonic w/ the blood plasma?
Explain your choice
- it is isotonic w/ the blood plasma
- example: severe hydration.
If you inject water directly, RBC will swell and burst (Haemolysis). This would be hypotonic.
In the I.V drip, there is 5% w/v glucose. This is nearly isotonic w/ blood plasma. As the glucose is metabolized, the water remains to rehydrate the body
60
How can milligram percent (quantitative method of finding concentration %) be helpful?
- blood urea nitrogen levels (BUN) level is measure in milligram %
- BUN is used for newborn babies to check that their kidneys are working properly. Urea nitrogen is a waste product that the kidneys remove from the blood. Higher than normal BUN levels indicate that your kidneys aren’t working well. A BUN test can help uncover the issue early on so that treatment can be more effective
61
What is the normal bun level?
7 - 21 mg urea / 100 mL blood
= 7 - 21 mg%
62
What is the name/condition that refers to an ‘elevated bun level’?
- azoremia
63
What can azotemia (elevated BUN level) be caused by?
- impaired renal function
- dehydration (lack of fluid volume to excrete waste products)
- excessive protein intake or protein catabolism
64
What is the blood urea level of an infant suffering dehydration?
- 32 mg%
(So 32 mg of urea per 100 mL of blood or 0.032 g of urea in 100 mL of blood = 0.032% w/v)
65
What is ppm (parts per million) method of finding concentration of solution used for? Give an example
- used to describe extremely dilute solutions
- for ex: the concentration of toxic metals present in drinking water. some cpds are toxic to humans at 1 ppm
66
What are redox reactions?
- rxns that produce energy at the molecular level of life
67
What are the 3 major purposes energy is required for?
- muscle contraction & other cellular movements
- active transport of molecules & ions
- synthesis of macromolecules & other bio molecules from simple precursors
68
Why cycle is the fundamental way of energy exchange in biological systems? Hint: it is the oxidation of food
ATP - ADP cycle
69
When does oxidation occur?
- when a molecule loses electrons, loses hydrogens, or gains oxygen
70
What happens if a molecule undergoes oxidation?
- it has been oxidized and said to be the reducing agent
71
When does a reduction occur?
- when a molecule does any of the following:
• gains e-
• gains hydrogens
• loses oxygen
72
What happens when a molecule undergoes a reduction?
- it has been reduced & is said to be the oxidizing agent
