Write electron configurations for the elements that are identified by these atomic numbers
a. 15
b.12
c.9
d.18

Answer: Three lithium ions are required to bond with one nitrogen ion.

Explanation:

Ionic compound is formed by the complete transfer of electrons from 1 atom to another atom.

The atom which looses the electron is known as electropositive atom and the atom which gains the electron is known as electronegative atom. This bond is usually formed between a metal and a non-metal.

Lithium is the 3rd element of the periodic table having electronic configuration of [tex]1s^22s^1[/tex]

This element will loose 1 electron to form [tex]Li^+[/tex] ion

Nitrogen is the 7th element of the periodic table having electronic configuration of [tex]1s^22s^22p^3[/tex]

This element will gain 3 electrons to form [tex]N^{3-}[/tex] ion

To form an ionic compound of lithium and nitrogen atoms, three lithium ions are needed to neutralize the charge on 1 nitrogen atom.

The chemical compound formed will be [tex]Li_3N[/tex]

Hence, three lithium ions are required to bond with one nitrogen ion.

Answer:

The elements in the second, third, fourth and fifth periods that have the same number of electrons with the highest energy level that barium are beryllium (Be) magnesium (Mg), calcium (Ca ) and strontium (Sr).

Explanation:

The Electronic Configuration of the elements is the arrangement of all electrons of an element in energy levels and sub-levels (orbitals). The filling of these orbitals occurs in increasing order of energy, that is, from the orbitals of lower energy to those of higher energy.

There are 7 energy levels, numbered from 1 to 7, and in which electrons are distributed, logically in order according to their energy level. Electrons with less energy will be spinning at level 1.

Valencia electrons are the electrons found in the last electronic layer (called valence orbitals). This electrons allows to determine their location in the Periodic Table. All elements of the same group have the same number of valence electrons (This does not occur in transition metals). The valence electrons increase in number as one advances in a period. Then, at the beginning of the new period, the number decreases to one and begins to increase again.

So, in summary, those elements that belong to a group have the same number of electrons in their last or last layers, and the group number indicates the electronic configuration of their last layer, varying only the period of the element.

On the other hand, periods represent the energy levels that an atom has. That is, an element with five layers or energy levels will be in the fifth period.

Given this, the elements in the second, third, fourth and fifth periods that have the same number of electrons with the highest energy level that barium are beryllium (Be) magnesium (Mg), calcium (Ca ) and strontium (Sr). This is because they are in the same group (they have the same number of electrons in their last layer)

The total change in internal energy would simply be calculated using the formula:

ΔU = -P (V2 – V1) + ΔH

where ΔU is the change in internal energy; P is constant pressure = 30 atm = 3,039,750 Pa; V2 is final volume = 2 L = 0.002 m^3; V1 is initial volume = 7.20 L = 0.0072 m^3; while ΔH is the heat = -74,400 J (heat released so negative)

Therefore:

ΔU =-3,039,750 Pa * (0.002 m^3 - 0.0072 m^3) + (- 74,400 J)

ΔU = - 58,593.3 J = - 58.6 kJ

Final answer:

When salt is added to water until no more dissolves, the solution becomes saturated and a dynamic equilibrium is established between the dissolved and undissolved salt. The water has reached its solubility limit, and though individual salt molecules continue to dissolve and precipitate, the visible amount of undissolved salt appears to remain constant.

Explanation:

When you add salt continuously to a glass of water, you will eventually notice that some salt will remain at the bottom because the solution has become saturated. This is a state where the water cannot dissolve any more salt at a given temperature and pressure, meaning you've reached the salt's solubility limit. At this point, a dynamic equilibrium is established between the undissolved salt at the bottom and the dissolved salt in the water. What this means is that the process of dissolution, where salt dissolves in water (NaCl(s) → NaCl(aq)), is still happening. Simultaneously, the reverse process, where dissolved salt precipitates out of the solution (NaCl(aq) → NaCl(s)), is also occurring at the same rate.

The forward and reverse processes balance each other out, so the total amount of dissolved salt in the water remains constant even as individual salt molecules continue to dissolve and precipitate. That's why the undissolved salt seems to be at a standstill at the bottom of the glass, even though the chemical reactions continue. This phenomenon demonstrates water's ability to dissolve substances up to a certain point, beyond which the excess material forms visible solid particles due to the lack of additional solvent capacity.

The mass of the sample of Calcium carbonate is 0.195g

The heat capacity formula,

[tex]\rm \bold{ Q= mC\Delta T}[/tex]\

Where,

Q- Heat absorbed = 45.5 J

C- specific heat capacity of  [tex]\rm \bold{ CaCO_3 = 0.82 J/g/^\cdot C }[/tex]

[tex]\rm \bold{ \Delta T}[/tex]- change in temperature = 280.5 k

m - mass = ?

Solving Equation for m

[tex]\rm \bold {m = \frac{45.5 J}{0.82\times 280.5 K } }\\\rm \bold {m = 0.195 g }[/tex]

Hence , we can conclude that the mass of sample is 0.195g.

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The amount in grams of water will be formed when 32.0 g H₂ is mixed with 32.0 g O₂ is 36 grams.

Moles from mass of any susbatnce will be calculated as:

n = W/M, where

W = given mass

M = molar mass

Given chemical reaction is:

2H₂  +  O₂  →  2H₂O

Moles of H₂ = 32g / 2g/mol = 16 mol

Moles of O₂ = 32g / 32g/mol = 1 mol

From the stoichiometry of the reaction, it is clear that

1 mole of O₂ = reacts with 2 moles of H₂

So in the given question, oxygen is the limiting reagent as hydrogen is present in excess quantity & predominated the formation of water.

1 mole of O₂ = produces 2 moles of H₂O

Now grams of water will be obtained by using mass-moles equation as:

W = (2mol)(18g/mol) = 36 grams.

Hence required mass of water is 36 grams.

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Answer:

dipole-dipole interactions

Explanation:

i said so :)

Answer:  Due to its shape

Explanation:  Polarity of any substance can be determined by its shape. It can also be determined by its dipole moment.

It has positive charge at its one end and negative charge on the other end.It has one oxygen atom which has negative charge (being electronegative in nature) and has two hydrogen atoms which has positive charge.

Thus electron charge density present on the hydrogen is being pulled by the oxygen mking it polar in nature.

The molecular geometry of PF3 (Phosphorus trifluoride) is trigonal pyramidal and it is a polar molecule due to the electronegativity differences between phosphorus and fluorine atoms forming polar bonds.

The molecular geometry of the PF3 molecule is trigonal pyramidal. The PF3 molecule contains one phosphorus atom and three fluorine atoms. Phosphorus has 5 valence electrons and fluorine has 7, so the PF3 molecule has 26 valence electrons in total. The phosphorus is at the center of the molecule, with the three fluorine atoms and one lone pair of electrons surrounding it. As a result, the molecule has a 'pyramid' shape with the phosphorus at the top.

In terms of its polarity, PF3 is a polar molecule. This is because the difference in electronegativity between the phosphorus and fluorine atoms creates a polar bond. The three polar bonds form a net dipole moment, making the entire molecule polar.

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The molecular geometry of the PF3 molecule is trigonal pyramidal, and this molecule is polar.

The PF3 molecule, which is phosphorus trifluoride, has a central phosphorus atom surrounded by three fluorine atoms. According to the VSEPR model, we count the electron pairs around the central atom, recognizing that there are three bonding pairs and one lone pair. Considering this, PF3 does not have a trigonal planar structure like BF3, which has no lone pairs, but instead has a trigonal pyramidal geometry. The presence of the lone pair on the phosphorus atom pushes the fluorine atoms down, which creates a pyramid-like shape rather than a flat plane. In addition, due to the differences in electronegativity between the fluorine atoms and the phosphorus atom, and the asymmetric shape of the molecule, PF3 has a net dipole moment, meaning it is polar.

Answer:

The correct answer is option b, that is, chemists have created medicine to fight leukemia.

Explanation:

An individual who does research associated with the chemicals is known as a chemist. The chemist performs the duty to guide the individuals with regard to chemical compounds and the qualitative analysis associated with it. A chemist does a specific role of performing research associated with chemical compounds and the procedures related to it. That is, a chemist performs extensive research associated with the field of chemistry. Therefore, in the given question, the creation of medicines to fight against leukemia will be the correct answer.