sem - 1 Flashcards
Who created the 1st periodic table & when?
- Dmitri Mendeleev published the 1st periodic table in 1869
How was Dmitri Mendeleev’s periodic table organized?
- organized in order of increasing atomic mass
- the new version of the P.T arranges the elements based on increasing atomic number
What similarities do elements within a group show?
- similar chemical properties & reactivity b/c they have the same number of valence electrons
Differentiate between metals & nonmetals.
- metals are great conductors of heat & electricity where as nonmetals are poor conductors of the two
Which groups on the periodic table have the most reactive elements?
- group 1 = alkali metals
- group 7 (VII) = halogens
What are valence electrons and what do they do?
- 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
What are the 3 factors that the attraction between the positive nucleus and valence electrons depend on?
1- number of protons in the nucleus
2- distance from the nucleus
3- shielding effect of other e- closer to the nucleus
What is the effective nuclear charge (Zeff)?
- 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-)
In the Zeff = Z - S (or sigma sign) formula, the sigma is called what?
- it is called the shielding constant & it is greater than 0 but less than ‘Z’
Zeff (effective nuclear charge) increases which ways on the periodic table?
- increases moving left to right
- increases moving down the periodic table (per slaters rule)
What is slaters rule?
- his rule calculates sigma (S) by accounting for the effective shielding of e- in each orbital shell
Define atomic radius.
- it is the distance between the nuclei of two combined/adjacent atoms
How does the atomic radius vary going left to right across a period? Why?
- 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)
How does the atomic radius vary going down a group? Why?
- 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.
What is ionic radius?
- 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)
How does the ionic radius change when we form an anion (X-)?
- 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.
How does the ionic radius change when we form an cation (X+)
- 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.
Define what isoelectronic is.
- 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
Is the ionic radius of a dispositive ion greater or less than the radius of a unipositive ion? Explain.
- 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
Is the ionic radius of a dinegetive ion larger or smaller than the radius of a uninegetive ion? Explain.
- 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-
We know that ions move through tiny channels in cell membranes. However, some channels allow ____ through but not larger than ____ ?
- allow Na+ through
- but not larger than K+
Define ionization energy (IE)
- it is the minimum energy required to remove the most loosely bound electron from a gaseous atom in its ground state.
Define and give examples of 1st VS 2nd VS 3rd ionization energies.
- 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-
How does ionization energy vary going across a period Vs down a group?
- 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.
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
Which group had the highest and lowest ionization energies?
- Alkali Metals (group 1) - lowest ionization energy
- Nobel Gases (group 8) - highest ionization energy
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-
What is the difference between high Vs low electron affinity?
- high EA = atom more easily accepts electron
- low EA = atom less easily accepts electron
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
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)
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
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
Describe the electronegativity trend on the periodic table.
- increases across a period (left to right)
- decreases going down a group
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
What is a diatomic molecule?
- a molecule that contains only 2 atoms
- ex: O2, H2, B2, Br2, HCl, CO
What is a polyatomic molecule?
- a molecule that contains more than 2 atoms
- ex: H2O, O3, NH3, CH4
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
What is atomic mass?
- the mass of the atom in atomic mass units (amu)
1 amu (atomic mass unit) is defined as what?
- a mass equal to 1/12 the mass of one carbon-12 atom
Define average atomic mass.
- the average mass of all the naturally occurring isotopes of the element.
- mass x abundance %
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
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
What is a chemical reaction?
- process in which a substance is changed into 1 or more new substances
What is Avogadro’s number?
6.022 x 10^23
1 mole of atoms = how many atoms?
1 mole of molecules = how many molecules?
• 6.022 x10^23 atoms
• 6.022 x10^23 molecules
What is molar mass?
- mass in grams of 1 mole of molecules or 1 mole of atoms
- unit for molar mass is g/mol
1 mole of atoms contains 6.022 x 10^23 atoms and has what kind of mass?
- atomic mass
1 mole of molecules contains 6.022 x 10^23 molecules and has what kind of mass?
- molecular mass
Difference between solute vs solvent?
- solute = substance being dissolved
- solvent = substance doing the dissolving
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
The human body is made up of what percentage of water?
- 60%
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
What is a solution concentration?
- the concentration of a solution is the amount of solute present in a given amount of solvent or solution
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
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)
Units of measure of water:
a) 1 ml = ? grams
b) density = ?
a) 1 gram
b) d = m/v
What is the Intravenous Drip (IV drip)?
- it is the giving of substances directly into a vein
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)
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
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
What is the normal bun level?
7 - 21 mg urea / 100 mL blood
= 7 - 21 mg%
What is the name/condition that refers to an ‘elevated bun level’?
- azoremia
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
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)
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
What are redox reactions?
- rxns that produce energy at the molecular level of life
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
Why cycle is the fundamental way of energy exchange in biological systems? Hint: it is the oxidation of food
ATP - ADP cycle
When does oxidation occur?
- when a molecule loses electrons, loses hydrogens, or gains oxygen
What happens if a molecule undergoes oxidation?
- it has been oxidized and said to be the reducing agent
When does a reduction occur?
- when a molecule does any of the following:
• gains e-
• gains hydrogens
• loses oxygen
What happens when a molecule undergoes a reduction?
- it has been reduced & is said to be the oxidizing agent
