Why:

The Modern wave-mechanical model describes an atom as being mostly empty space with a nucleus containing all of the positive charge.  Unlike the Bohr model which placed the electrons in elliptical orbits around the nucleus, the Wave model describes the electron's position as uncertain and simply describes three dimensional regions of space (orbitals) in which you are most likely to find an electron.

The Bohr model quantized the electron's energy by where it was in its orbit in relation to its proximity to the nucleus.  However, the modern wave-mechanical model quantized the electron's energy by "what" orbit the electron is in, not where it was in the orbit.  The electron's energy stays constant while in its orbital, and it is actually the movement from one orbit to another that either absorbs or releases energy.  Electrons tend to remain in their lowest energy orbital unless they are excited. It is this new Modern wave- mechanical model that gives the electron both a wave-like and particle-like description.

Answering this question:

Remembering that the nucleus is comprised of protons and neutrons immediately allows you to eliminate answers (1) and (2) even if you don't remember what the Wave Model says exactly or you don't remember the difference between the Wave-mechanical model and the Bohr model.

A positron is the antimatter equivalent of an electron and is incredibly rare.  Another way to describe a positron is that its a positively charged electron.  Remembering this would help you eliminate (4) almost immediately.  However, even if you didn't remember what a positron was its unfamiliarity would be a warning sign that it probably should not be included in an atomic model.

Which thereby leaves you with (3) as your answer.

Correct Answer: (4) the same quantity of charge and the opposite sign

Why:

An atom consists of protons, neutrons, and electrons. A proton is a subatomic particle found in the nucleus of an atom. An electron is a subatomic particle found orbiting the nucleus of an atom.  The proton carries an electric charge of +1 while an electron carries an electric charge of -1.  Therefore the proton has the same quantity of charge with the opposite sign of an electron.

Answering this question?

You may remember learning that an uncharged element has an equal number of protons and electrons to balance the charge out to zero.  Therefore it would only make sense that the charges must be equal and opposite which immediately leaves only (4) as the answer.  It may also be helpful to remember that where protons and electrons do differ is in size and weight.  Protons weigh substantially more, however that does not affect the quantity or sign of the charges.  They are equal and opposite.

Correct Answer: (1)

Why:

An isotope of an element is the same chemical element with a different composition of protons and neutrons in its atom. Each isotope has the same atomic number (number of protons) but has a different number of neutrons thereby changing the atomic mass.  The standard way of writing this is to put the new atomic mass as the superscript (top) and the original atomic number as the subscript (bottom) followed by the elements proper abbreviation.  It is also common to leave out the atomic number because it stays the same from isotope to isotope and is implied implicitly in the abbreviation of the element.  For example (3) could also be written as simply ¹⁹O.

In conclusion isotopes are the same basic chemical element with a different number of neutrons in the atom, making (1) the only possible answer.

Answering this question:

The key to answering this question is to remember what an isotope is.  However, even if you only remember that an isotope is a different version of the same element this question is solvable.  You can immediately eliminate (3) and (4) because they are different elements altogether.  You may not remember what exactly is different about an isotope but when left with choices (1) and (2) it may not hinder you.  Looking at (2) it becomes clear that those are the exact same elements with no change at all, and we remembered that an isotope had some kind of change.  This leaves us with (1) as the only possible correct answer.

Correct Answer: (1) gains an electron and its radius increases

Why:

The ionic radius of an ion is the distance from the nucleus to the point at which the nucleus has influence on the electron cloud.

Whenever an atom loses an electron it becomes a cation.  A cation is always smaller than its parent atom because there is now a strong positive charge in the nucleus pulling on less of a negative charge (because one electron was taken away).

This makes the positive nucleus more overpowering to the remaining electron and it will pull the electron in closer making the ion smaller.

When an atom gains an electron it becomes an anion.  An anion is always bigger than its parent atom because there is now a stronger negative charge (because an extra electron is present) and the positively charged nucleus can no longer attract the electrons as effectively which results in and expansion of the electronic cloud.

In order for Chlorine to become a negative ion it must gain a negative charge or an electron. Therefore it would have the properties of an anion and answer (1) is correct.

Answering this question:

It should be rather inherent that for a chlorine atom to become negative it has to gain a negative charge or an electron which immediately allows us to eliminate answers (3) and (4).  You may not know whether the radius increases or decreases but you've doubled your chances in getting a correct answer.  The only way to eliminate answer (2) is to know that adding a negative charge will repel the other valence electrons and cause the radius to get bigger, therefore leaving you with answer (1).

*Correct Answer (1) N

Why:

Electron negativity is the chemical property that quantifies an atoms ability to attract electrons to itself in covalent bonds.  The higher an atoms' electron negativity is the stronger its attraction to electrons would be.  So for this question you simply need to locate Table S and find which element has the highest number.  The correct answer is (1) Nitrogen.

Answering this question:

This should be as straightforward as looking at the chart and choosing the highest electron negativity.  However, if you become unsure of which number to look for, take a logical look at the Table S.  Most of those properties you will recognize such as density and melting point.  Eliminate those that you can, and look for a trend in the others.  For example, though this will not always work, you could confuse electron negativity and ionization energy and obtain the correct answer either way.

Correct answer: (2) increases

An atom is the fundamental building block of matter.  It has smaller components called subatomic particles which are the: proton, neutron and electron.

The proton and neutron are both found in the center of the atom called the nucleus.  The former has a positive charge while the latter has no charge.  On the other hand, the negatively-charged electron is found in orbitals while circling around the nucleus.  The electron's lowest possible energy is called the ground state in which this is the normal energy level.

Answering the question:

When energy decreases from one orbital to another, the movement of the electron is from an excited state to its ground state, thus, eliminating option no. 1.  When there is no change in the energy level, the state of the atom remains unchanged.  There will be no excitation stage expected which makes option no. 3 invalid.

When an electron receives and absorbs extra energy from heat, light or even from a collision with a nearby atom or particle, it moves to a higher orbital with higher energy level.  This higher orbital is now the electron's excited state.  For this underlying concept, option no. 2 is the correct answer for the question.

The total number of valence electrons in an atom of Mg-26 in its ground state is two (2).

The ground state of any element is that state at which it possesses the least amount of energy. In this state the attraction between the nucleus and the surrounding electrons is sufficient to prevent electrons from escaping.

Answering the question:

In order to correctly answer this question we need to understand the meaning of the term valence. Valence refers to the number of electrons available to bonding found in the outermost orbital of an element. The above diagram has 2 electrons present in its outermost orbital, hence the total number of valence electrons is two. The inner negatively charged electrons are physically closer to the positively charged nucleus and result in very tightly packed inner orbital of electrons.

Correct Answer:

Innermost Shell - 2 electrons

Middle shell - 8 electrons

Outermost Shell - 0 electrons

Magnesium 26 is categorized as an alkaline earth metal and falls in group 2 of the periodic table. This class of elements generally will "give up" their valence electrons when they enter an excited state of the correct energy. An excited state is any state higher than the ground state. According to the modern wave mechanical model electrons in a lower orbital will move to a higher orbital when provided with sufficient energy (excited). This is in contrast to the non-metal group of elements, which are very reactive and will receive electrons in there outermost orbital.

Answering the question:

In order to answer the question it helps to know the groups of elements in the periodic table, ranging from metals to non-metals. The first two columns are the alkali metals and alkaline earth metals. There groups have the tendency to give up there valence electrons when excited sufficiently. This would result in the valence electrons receiving sufficient energy and move to a high enough orbital such that the nucleus no longer possesses sufficient attractive force to hold the valence electrons in orbital.

The number of valence electrons present is indicated by the group in which the elements occur. Since magnesium (Mg) is a member of the metals group we know it will have the tendency to give up its electrons, based on the diagram there are two electrons in its valence orbital. The result would be magnesium with two more protons than electrons and hence a net positive charge represented by Mg²⁺. The electrons of the two inner orbitals would be the only remaining electrons resulting in the configuration in the answer above.

**Correct Answer:

Cl₂ + 2e → 2Cl^-

Cl-Cl + → 2 Cl

Answering the question:

The Lewis electron-dot diagram is a diagram showing the electron count of an element in the valence orbital of the element and how electrons will migrate when reacting. In the case of Cl, it is a halogen belonging to group 17 in the periodic table. This group of elements has 7 electrons in their valence orbital.  This makes them good electron acceptors.

Example Answer:

1)      The atom has heavy compact central body or nucleus

2)      The atom is composed of mostly empty space

Answering the Question: