b. exposure to toxic chemicals
c. the net charge of the atom
d. the attraction of protons to electrons
e. an unstable ratio of protons and neutrons
The answer is: e. an unstable ratio of protons and neutrons.
Neutrons stabilize the nucleus, because they attract protons and reduce electrical repulsion between protons.
The larger is neutron-proton ratio, the higher is probability for nuclear decay.
Ratio of protons to neutrons in a stable atom is 1 : 1.
For example, nitrogen atom (N-14) has 7 protons (p⁺) and 7 neutrons (n°). The neutron–proton ratio (N/Z ratio or nuclear ratio) is 7 : 7 ( 1 : 1 ).
Another example, neon atom (Ne-20) has 10 protons (p⁺) and 10 neutrons (n°). The neutron–proton ratio is 10 : 10 ( 1 : 1 ).
The neutron–proton ratio generally increases with increasing atomic number.
(2) Mg (4) Ba
Barium (Ba) has the lowest first ionization energy among the given elements of group 2. Therefore, option (4) is correct.
The ionization energy is the minimum amount of energy that is required to knock out an electron in a gaseous atom or ion. Ionization energy can also be used to estimate the strength of chemical bonds and is measured in units of electronvolts or kJ/mol.
Alkaline earth elements can lose both valence electrons to attain a noble gas configuration. So, these elements have two ionization energies. 1st ionization energy of alkaline earth metals is the energy required to remove the first electron from the neutral atom.
With increasing atomic size down the group, the valence electron gets shielded by the inner electrons. So they can easily be removed with less energy. Hence the first ionization energy of group 2 elements decreases with an increase in the atomic number or atomic size.
Therefore, Barium has the lowest first ionization energy.
Learn more about ionization energy, here:
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a. True
b. False
B. Kryptonite
C. Quartz
D. Pyrite
A black hole collapsed to form the sun; small planetary objects formed; small planetary objects collided with each other to form larger objects.
B.
Most of the dust and gas contracted into a central mass—the Sun; half the mass of the cloud condensed to form Jupiter; asteroids and comets crashed into the sun to form the smaller planets.
C.
A spinning cloud of dust began to compress to form the sun; small planetary objects formed; hydrogen and helium became concentrated in the outer solar system to form the outer planets.
D.
Gravitational force held the newly formed planets around the sun; small planetary objects formed; hydrogen and helium became concentrated in the outer solar system to form the outer planets.
The statement about the formation of the solar system that are true and in a correct order are Gravitational force held the newly formed planets around the sun; small planetary objects formed; hydrogen and helium became concentrated in the outer solar system to form the outer planets. The answer is letter D.