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nikdorinn [45]
3 years ago
13

J.J. Thomson's plum pudding model of the atom followed the discovery of

Chemistry
2 answers:
bixtya [17]3 years ago
6 0

Answer:

A

Explanation:

Got it right:)

Rama09 [41]3 years ago
3 0
The answer is A i think from the options though the answers are worded a bit weird
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Essential amino acids cannot be made
sattari [20]

Answer:

True

Explanation:

There are 9 essential amino acids which cannot be made by the body and have to be obtained from food.

They are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine

4 0
2 years ago
Suppose a laboratory wants to identify an unknown pure substance. The valence electrons of the substance's atoms feel an effecti
zalisa [80]

Answer:

  • The answer is the third option in the list:<em> It would have smaller atomic radii than Si and higher ionization energies than Si.</em>

Explanation:

The<em> effective nuclear charge</em> is that portion of the total nuclear charge that a given electron in an atom feels.

Since, the inner electrons repel the outer electrons, t<em>he effective nuclear charg</em>e of a determined electron is the sum of the positive charge (number of protons or atomic number) that it feels from the nucleus less the number of electrons that are in the shells that are are closer to the nucleus than the own shell of such (determined) electron.

Mathematically, <em>the effective nuclear charge (Zeff)</em> is equal to the atomic number (Z) minus the amount (S) that other electrons in the atom shield the given (determined) atom from the nucleus.

  • Zeff = Z - S.

Since, the valence electrons are the electrons in the outermost shell of the atom, you can find certain trend for the value Zeff.

Let's look at the group to which Si belongs, which is the group 14. This table summarizes the relevant data:

Element   Z   Group   # valence electrons     S                      Zeff = Z - S

C              6      14                      4                     6 - 4 = 2             6 -  2 = +4

Si             14     14                      4                     14 - 4 = 10         14 - 10 = +4

Ge           32     14                     4                     32 - 4 = 28       32 -28 = +4

Sn           50     14                     4                     50 - 4 = 46       50 - 46 = +4

Pb           82     14                     4                     82 - 4 = 78        82 - 78 = +4  

With that, you have shown that the valence electrons of the unknown substance's atoms feel an effective nuclear charge of +4 and you have a short list of 4 elements which can be the unknown element: C, Ge, Sn or Pb.

The second known characteristic of the unknown substance's atoms is that it has a <em>higher electronegativity than silicon (Si)</em><em>.</em>

So, you must use the known trend of the electronegativity in a group of the periodic table: the electronegativity decreases as you go down in a group. So, three of the elements (Ge, Sn, and Pb) have lower electronegativity than Si, which has left us with only one possibility: the element C. The valence electrons of carbon (C) atoms feel an effective nuclear charge of +4 and it carbon has a higher electronegativity than silicon.

Other two periodic trends attending the group number are the <em>atomic radii and the ionization energy</em>.

The atomic radii generally increases as you go from top to bottom in a group. This is because you are adding electrons to new higher main energy levels. So, you can conclude that the originally unknwon substance (carbon) has a smaller atomic radii, than Si.

The ionization energies generally decreases as you go from top to bottom in a group. This os due to the shielding effect: as seen, the effective nuclear charge of the atom's valence electrons remains constant, while the distance of the electrons from the nucleus increases (the valence electrons are farther away from the nucleus), which means the upper the element in a given group, the larger the ionization energy of the atoms.

With this, our conclusions about the unnkown substance are:

  • Since it has a higher electronegativity value than silicon (Si), it is right up of Si, and there is on only element possible element than can be (C).

  • Since, it is upper than silicon (Si), it would have smaller atomic radii.

  • Due to the shielding effect, it would have larger ionization energies.

  • The answer is the third option in the list: It would have smaller atomic radii than Si and higher ionization energies than Si.

6 0
2 years ago
Can an ion be either positive or negative? True or False
vekshin1

Answer:

True

Explanation:

3 0
2 years ago
PLZ HELP PLZ PLZ ILL MARK AS BRAINLIESTT!!!!
LuckyWell [14K]

Q.1-

Given,

mass - 10grams

volume - 24 cm³

density = mass/volume

density = 10/24

density = 0.416 g/cm³

Q.2-

Given,

mass - 700grams

volume - 1100cm³

density = mass/volume

density = 700/1100

density = 0.6363 g/cm³

5 0
3 years ago
Calculate the molarity 20ml of 3.5 m kci in to a final volume of 100 ml​
satela [25.4K]

Answer:

Molarity =  0.7 M

Explanation:

Given data:

Volume of KCl = 20 mL ( 0.02 L)

Molarity = 3.5 M

Final volume = 100 mL (0.1 L)

Molarity in 100 mL = ?

Solution:

Molarity = number of moles of solute / volume in litter.

First of all we will determine the number of moles of KCl available.

Number of moles = molarity × volume in litter

Number of moles = 3.5 M × 0.02 L

Number of moles = 0.07 mol

Molarity in 100 mL.

Molarity = number of moles / volume in litter

Molarity =  0.07 mol /0.1 L

Molarity =  0.7 M

3 0
3 years ago
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