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>
The answer is (4) Ag(s)
Solid Silver has a Face Centered Cubic crystal structure.
The remaining choices are gases (H2 & Ar) and liquid (Br). Liquids and gases do not form crystal structures as their atoms are loose.
We have mass. Anything that generally includes atoms is matter
Answer: 9.09 %
Explanation:
To calculate the percentage concentration by volume, we use the formula:
Volume of ethanol (solute) = 30 ml
Volume of water (solvent) = 300 ml
Volume of solution= volume of solute + volume of solution = 30+ 300 = 330 ml
Putting values in above equation, we get:
Hence, the volume percent of solution will be 9.09 %.
Answer:subtropical highs. ... Near the poles the pressure is high and it is known as the polar high. These pressure belts are not permanent in nature
Explanation: The horse latitudes are subtropical regions known for calm winds and little precipitation. ... Unable to sail and resupply due to lack of wind, crews often ran out of drinking water. To conserve scarce water, sailors on these ships would sometimes throw the horses they were transporting overboard.
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