What part of Earth contains rocks?

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: It would have smaller atomic radii than Si and higher ionization energies than Si.

Explanation:

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

Since, the inner electrons repel the outer electrons, the effective nuclear charge 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, the effective nuclear charge (Zeff) 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 higher electronegativity than silicon (Si).

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 atomic radii and the ionization energy.

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

A student is worried about determining if a chemical is radioactive. Which

Mamont248 [21]

Answer:

Hazards Identification

Explanation:

A safety data sheet, SDS, is an informational document provided by the manufacturer or importer of a hazardous chemical detailing the chemical, physical, health, and environmental health hazards associated with the chemical as well as safety precautions in handling the chemical.

Some of the sections in the SDS include:

Product Information: It identifies the chemical as well as its recommended uses. The contact information of the manufacturer is also provided.

Fire fighting methods: It gives measures and guidelines necessary for fighting a fire caused by the chemical.

Physical and chemical properties: states the physical and chemical properties of the chemical substance such as: appearance, odor, pH, melting/freezing point, boiling point and boiling range, flammability, etc.

Hazards identification: states the hazards of the chemical and the necessary warnings regarding the hazards. Some of the information provided include: hazard classification of the chemical (for example flammable liquid, oxidizing gases,explosives, etc), signal word, hazard statement (for example radioactive), pictograms, precautionary statements, etc.

From the above information provided, the student should refer to the hazards identification section.

8 0

3 years ago

How does the location of mesosaurus fossils support the theory of continental drifts?

Ratling [72]

Answer:

For this reason, the existence of Mesosaurus helps support the theory of continental drift; that is, the now-well-attested fact that South America and Africa were joined together into the giant continent Gondwana 300 million years ago before the continental plates supporting them broke apart and drifted.

Explanation:

3 0

2 years ago

Answer (example of a bar graph)

Vilka [71]

Here's an example of a bar graph.

3 0

3 years ago

The mass of the erlenmeyer flask alone is 88.000 grams. calculate the mass of the zinc and hcl after the addition of 25 grams of

arsen [322]

If concentration of HCl is 1 mol/dm³ :
m(erlenmeyer flask) = 88,00 g.
m(Zn) = 25,0 g.
V(HCl) = 15 ml = 15 cm³ = 0,015 dm³.
Chemical reaction: Zn + 2HCl → ZnCl₂ + H₂.
n(HCl) = c(HCl) · V(HCl).
n(HCl) = 1 mol/dm³ · 0,015 dm³ = 0,015 dm³.
n(Zn) = 25 g ÷ 65,4 g/mol = 0,38 mol.
n(H₂) = 0,015 mol ÷ 2 = 0,0075 mol.
m(H₂) = 0,0075 mol · 2g/mol = 0,015 g.

7 0

3 years ago