Answer:
A chemical change because a temperature change occurred, the solid disappeared and a gas was produces
Explanation:
Magnesium reacts with hydrochloric acid releasing energy, and leading to the formation of magnesium chloride and hydrogen gas. This is represented by the equation below:
Mg₍s₎ + 2HCl₍aq)⇒ MgCl₂₍aq₎ + H₂₍g₎
Answer:
1) Ca: [Ar]4s²
2) Pm: [Xe]6s²4f⁵
Explanation:
1) Ca:
Its atomic number is 20. So it has 20 protons and 20 electrons.
Since it is in the row (period) 4 the noble gas before it is Ar, and the electron configuration is that of Argon whose atomic number is 18.
So, you have two more electrons (20 - 18 = 2) to distribute.
Those two electrons go the the orbital 4s.
Finally, the electron configuration is [Ar] 4s².
2) Pm
The atomic number of Pm is 61, so it has 61 protons and 61 electrons.
Pm is in the row (period) 6. So, the noble gas before Pm is Xe.
The atomic number of Xe is 54.
Therefore, you have to distribute 61 - 54 = 7 electrons on the orbitals 6s and 4f.
The resultant distribution for Pm is: [Xe]6s² 4f⁵.
Answer:
The number of protons is equal to the mass number of the element. Since an element always has a different number of protons, the mass can indicate how many neutrons are in an isotope. Atoms of the same element can have a different number of neutrons. There are three naturally-occurring isotopes of carbon.
Explanation:
Answer:
The metric system uses units such as meter, liter, and gram to measure length, liquid volume, and mass, just as the U.S. customary system uses feet, quarts, and ounces to measure these.
Volume: 1 liter is a little more than 1 quart
Mass: 1 kilogram is a little more than 2 pounds
Length: 1 centimeter is a little less than half an
Explanation:
The atomic number (Z) of the 3 elements F, Ne, and Na, are 9, 10, and 11.
Explanation:
Now Z refers to the number of protons in the element's nucleus, and protons are POSITIVELY charged particles. So a fluoride ion, F−, has 10 electrons rather than 9 (why?), a neutral neon atom has 10 electrons, and a sodium ion, Na+, also has 10 electrons (why?).
So the 3 species are ISOELECTRONIC; they possess the same number of electrons.
You should look at the Periodic Table to confirm the electron number. Elements are (usually) electrically neutral (sometimes they can be ionic if they have lost or gained electrons). If there are 10 positively charged protons in the nucleus, there are NECESSARILY 10 electrons associated with the NEUTRAL atom. I don't know WHY I am capitalizing certain WORDS.
You might ask why sodium will form a positive ion, Na+, whereas F forms a negative ion, F−. This again is a Periodic phenomenon, and explicable on the basis of the electronic structure that the Table formalizes.
Neutral metals tend to be electron-rich species, which have 1 or more electrons in a valence shell remote from the nuclear charge. On the other hand, neutral non-metals have valence electrons in incomplete shells, that do not effectively shield the nuclear charge. The demonstrable consequence is that metals lose electrons to form positive ions, whereas non-metals gain electrons to form negative ions.
