Search found 28 matches

by 304984981
Sun Jun 10, 2018 11:53 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 9
Views: 378

Re: Bond Length

it's just a general knowledge and is always true.
double bond is longer than triple bond but shorter than single bond.
by 304984981
Sun Jun 10, 2018 11:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Atoms in a Plane
Replies: 4
Views: 226

Re: Atoms in a Plane

as long as the pi bond exist, the double bond(which contains pi bond and connects two atoms) can't not rotate, so they must be in the same plane.
by 304984981
Sun Jun 10, 2018 11:45 pm
Forum: Hybridization
Topic: Chapter 4 [ENDORSED]
Replies: 4
Views: 268

Re: Chapter 4 [ENDORSED]

as long as they show a symmetrical geometry, and all bonds connect to the same element. it's non-polar
by 304984981
Sun Jun 03, 2018 2:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: cis and trans
Replies: 7
Views: 216

Re: cis and trans

cis molecule has same types of atoms on the same side.
trans molecule has same types of atoms on the opposite sides.
So, even the polar bonds exists, but the trans molecule is non-polar in general since they oppositely arranged atoms' dipole moments cancel out.
by 304984981
Sun Jun 03, 2018 1:58 pm
Forum: Naming
Topic: Coordination compound
Replies: 6
Views: 298

Re: Coordination compound

Coordination compound is where Ligands( lone pairs donar,lewis base)attached to a Transition Metal ion that forms coordinative bonds between them. Ligands can be differnet kinds, as long as they have long pairs of electrons to donate. They can be anions like Cl-,Br-,F-, they can also be neutral e.g....
by 304984981
Sun Jun 03, 2018 1:54 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligands
Replies: 8
Views: 279

Re: Ligands

they have to use lone pairs to form coordinative bondS with the TM ion.

Monodentate ligand is a lewis base that donates one lone pair of electrons to a TM ion to form a bond.
Biodentate ligand is a lewis base that donates 2 lone paris of electrons to a TM ion to form 2 bond.
by 304984981
Sun May 27, 2018 9:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Ammonia shape [ENDORSED]
Replies: 2
Views: 106

Re: Ammonia shape [ENDORSED]

NH3 has 4 regions of electron density, 3 of them are bonding pairs and 1 of them are lone-pairs. AX3E1 Although it is arrangded tetrahedrally, but the way to minimize the repulsion betweena atoms rearrange the atoms to form a TRIGONAL PYRAMIDAL shape Why we call it pyramidal? since it looks like a p...
by 304984981
Sun May 27, 2018 9:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: shape of water
Replies: 8
Views: 209

Re: shape of water

Water molecule has a BENT SHAPE Although it has 4 regions of electronic density, which mean it is arranges tetrahedrally But 2 of the regions are because of lone pairs, while 2 others are bonding pairs So it causes a larger repulsion than the tetrahedral(109.5), also larger than the trigonal pyramid...
by 304984981
Sun May 27, 2018 9:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR
Replies: 3
Views: 129

Re: VSEPR

no matter what type of bond is occurring, you just consider it as a single bond, which means yes, one double bound is still AX
That's why we said in VSEPR model, the resonance does not matter.
by 304984981
Sun May 20, 2018 8:04 pm
Forum: Dipole Moments
Topic: London Dispersion, Induced dipole- Induced dipole, Van Der Waals
Replies: 5
Views: 192

Re: London Dispersion, Induced dipole- Induced dipole, Van Der Waals

no, there is no difference.
As professor mentioned, all of them 3 describe the same thing, but the induced dipole-induced dipole is the best one that demenstrartes what's actually going on.
by 304984981
Sun May 20, 2018 8:02 pm
Forum: Electronegativity
Topic: Relationship between Electronegativity and Ionization Energy
Replies: 4
Views: 798

Re: Relationship between Electronegativity and Ionization Energy

actually the trend of electronegativity and first ionization energy is the same but just keep In mind there are several exceptions
for example, the first ionization energy of N is actually larger than O
by 304984981
Sun May 20, 2018 7:58 pm
Forum: Electronegativity
Topic: Isoelectronic [ENDORSED]
Replies: 11
Views: 596

Re: Isoelectronic [ENDORSED]

it means all atoms with same number of electrons
for exmaple Na has 19 electrons but Mg has 20 electrons, so they are not isoelectronic
but Na and Mg- are isoeletronic since Mg- has 20 electrons as well
by 304984981
Sat May 12, 2018 2:41 pm
Forum: Trends in The Periodic Table
Topic: Ionization exceptions [ENDORSED]
Replies: 8
Views: 767

Re: Ionization exceptions [ENDORSED]

all the elements in the 5th and 6th column (N,O,S,P...) share the same trend exceptions, which means N>O, P>S. because of the half-filled p-orbital is stable All elemetnts in the 4th and 5th column(Mg,Al..) share the same trend excpetion, which means Mg>Al, becuas of full-filled of p-orbital is stable
by 304984981
Sat May 12, 2018 2:22 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: What does ground state mean? [ENDORSED]
Replies: 4
Views: 236

Re: What does ground state mean? [ENDORSED]

ground state means a normal performance of an atom, which means the atom itself is not excited by external force. Just think about water for example, under normal conditions, it's "ground state" is liquid. But if you increase the temperature to boil it, it get "excited" and turns...
by 304984981
Sat May 12, 2018 2:19 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: electron configuration of chromium? [ENDORSED]
Replies: 3
Views: 185

Re: electron configuration of chromium? [ENDORSED]

copper and chromium are the only 2 exceptions that disobeys the regular rules you need to remember for this course.
For copper and chromium, the 3d orbital is half-filled or fully-filled since they wanna get more stable.
by 304984981
Sun May 06, 2018 2:04 pm
Forum: DeBroglie Equation
Topic: When to use DeBroglie or Ek equation
Replies: 7
Views: 298

Re: When to use DeBroglie or Ek equation

Any moving mass will have a wavelike property with wavelength of λ, this equation is DeBroglie Equation which is λ=h/mv
however light does not have a mass so, it's not feasible to light(photons)

The more massive of a subject, it's visible wavelength is lower. So it will become undetectable.
by 304984981
Sun May 06, 2018 2:00 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: In class problem [ENDORSED]
Replies: 6
Views: 338

Re: In class problem [ENDORSED]

light is the fastest speed in the whole universe
according to the General Relativity. If there is something faster than light...then the whole theories of physic will collapse!
so if the value of speed you calculated is faster than 3E8, it's unrealistic
by 304984981
Sun May 06, 2018 1:09 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: HW #1.43
Replies: 8
Views: 447

Re: HW #1.43

just remember P=mv where m is a constant which is the mass of a electron, 9.11E-31 kg And according to Heisenberg Indeterminacy (Uncertainty) Equation: px=h/4pi, and because p=mv, so mvx=h/4pi put in all the variable, where m=9.11E-31, x=350pm=350E-12 m, h=6.63E-34, we get the final answer 165469.22...
by 304984981
Mon Apr 30, 2018 4:28 pm
Forum: Trends in The Periodic Table
Topic: Radius
Replies: 6
Views: 298

Re: Radius

The ionic radius is between ionic compound, such as NaCl, KCl. Atomic radius is between neighbouring atoms, for example metal Mg, Fe By the way, covalent radius measn 2 nonmetal joined by the covalent bond, eg, oxygen, Nitrogen Howeverever, dont care much about it because all radiuses follow the sam...
by 304984981
Mon Apr 30, 2018 4:21 pm
Forum: Trends in The Periodic Table
Topic: ionization energy
Replies: 3
Views: 109

Re: ionization energy

Are you talking about the first ionization energy? if it is, then the first ionization energy increases across the period and decreases down the group Reasons for that is because of 1. proton numbers which determine the nuclear attraction 2. number of shells which determined by the number of electro...
by 304984981
Mon Apr 30, 2018 4:18 pm
Forum: Trends in The Periodic Table
Topic: atomic mass
Replies: 3
Views: 100

Re: atomic mass

Typically larger the atomic number(more protons), the more massive the atom will be. Because the atom is composed of electrons, which basically have no or little mass, and proton & neutrons. The mass of atom is focus on the nucleus, in other words, the nucleus( proton & neutron) determines t...
by 304984981
Sun Apr 22, 2018 6:52 pm
Forum: Photoelectric Effect
Topic: Wave vs. Particle
Replies: 8
Views: 195

Re: Wave vs. Particle

light is descried as a wave because it has interference, diffraction. Details seen Thomas Young Experiment
Light is described as a particle because of photoelectric effect, which demonstrates that the intensity does not affect the amount of electrons get out, but wavelength/frequency does.
by 304984981
Sun Apr 22, 2018 6:43 pm
Forum: Properties of Light
Topic: frequency and wavelength [ENDORSED]
Replies: 5
Views: 209

Re: frequency and wavelength [ENDORSED]

The first thing you need to know is that all electromagnetic radiation, including light, follows the equation C=frequency x wavelength, where C is the constant, that is the speed of light.(Proper estimated value 3E8) So, whatever it happens, C is never changing. Always be equal to 3E8 Acoording to t...
by 304984981
Sun Apr 22, 2018 6:39 pm
Forum: Properties of Light
Topic: Speed of Light which is more accurate? [ENDORSED]
Replies: 6
Views: 211

Re: Speed of Light which is more accurate? [ENDORSED]

in reality, the light's speed is less than 3E8. But 2.998E8 is much more complicated to calculation and maybe difficult to evaluate. Considered about above, we use 3E8 in calculation since there is not much difference. So, yes , 2.998E is actually more accurate, but not convenient for massive calcul...
by 304984981
Sun Apr 22, 2018 6:33 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect on different material? [ENDORSED]
Replies: 2
Views: 92

Re: Photoelectric Effect on different material? [ENDORSED]

we need material in which the electrons are mobilized--means they have free moving electrons.
Therefore, any materail that has free-moving electrons are good for this experiment. But the metal is one of these cases
by 304984981
Tue Apr 10, 2018 11:41 am
Forum: Empirical & Molecular Formulas
Topic: Formula steps
Replies: 4
Views: 205

Re: Formula steps

pretty easy
always remember this equation: known molar mass/molar mass from empirical formula
by 304984981
Tue Apr 10, 2018 11:32 am
Forum: SI Units, Unit Conversions
Topic: Units + their meanings
Replies: 3
Views: 154

Re: Units + their meanings

mol is a unit, that saying 6.02E23 molecules is inside. So when I say one mole of atoms(molecules), it means there are 6.02E23 atoms(molecules). Atomic mass is the property of an element, as you can see on the periodic table, each element has specific atomic mass. For example, for O is 16 and H is 1...
by 304984981
Tue Apr 10, 2018 11:26 am
Forum: SI Units, Unit Conversions
Topic: Sig figures
Replies: 9
Views: 323

Re: Sig figures

if in the question the number is 0.500g for example, then all your calculation must be in 3 significant figures.

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