Answer:
D. 4
Explanation:
Answer and Explanation: Carbon can form a maximum of four covalent bonds. Carbon can share up to four pairs of electrons, therefore, the carbon atom fills its outer energy level and achieves chemical stability.
Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
Answer:
Crossing over Mitosis
Explanation:
A process called meiosis ensures siblings share just about 50% of their genotype. That's how siblings can have different DNA. Meiosis is a form of cell division that is only used to produce a special category of cells, called gametes.
