Periodic Table

This is a great question. Actually before 1961 12C had a different mass than it has today. The mass scale we use is actually relative and before 1961 the mass scale was based on Oxygen so 16O = 16 which was the standard in place since 1906. In the 20's people started to discover oxygen isotopes and the chemists 16O scale was not the same as the physicists 16O scale , so it was decided to settle on Carbon to make both the physicists and chemists happy

Check the related link below for the complete history of what happened

The symbol for carbon is C and its atomic number is 6.

Krypton is a component of the Earth atmosphere.

Every type of atom currently know to man. It consists of 118 elements, though the number is always changing.

iradium is the precious metal element apart from platinum

The group of the periodic table that contains the gases is Group 18, also known as the noble gases. These gases include helium, neon, argon, krypton, xenon, and radon, which are all colorless, odorless, and have very low chemical reactivity.

To create a total charge of zero, lithium with an atomic number of 3 (Li) needs to lose one electron to form Li+ with a charge of +1. Fluorine with an atomic number of 9 (F) needs to gain one electron to form F- with a charge of -1. Therefore, one atom of lithium and one atom of fluorine are needed to create a compound with a total charge of zero.

Elements with similar properties are usually located in the same Group (column) on the Periodic Table.

Groups on the periodic table are called families because elements within the same group share similar chemical properties due to having the same number of valence electrons. This similarity in properties is what defines them as a family.

The element with atomic number 119 is a theoretical element and hasn't been observed. However, it does still have an IUPAC systematic placeholder name; which is Ununennium (Uue). Only one attempt has ever been made to make this element. That was in 1985, when Calcium-48 ions were bombarded at Einsteinium-254. It was a failure. If it were to be discovered, it would be the first element of period 8 and would probably fit in under Francium.

A group is a vertical column in the periodic table; there are 8 groups, numbered, always in Roman numerals, I to VII from left to right, with group O (the noble gases) on the far right-hand side. The atoms of elements within any given group have similar outer electron configurations

The elements in each column of the periodic table have generally similar chemical properties, except that in columns 8 through 10, the elements in each row are at least as similar to one another as those in the same columns in other rows.

a soild, melting point 97.72 °C,

room temperature is 20°C

MP > 20 therefore a solid

Hydrogen has properties of both Group 1 and Group 17 elements, making its classification ambiguous. It does not exhibit typical Group 1 characteristics such as similar chemical reactivity to alkali metals or easily losing its electron to form a cation. Additionally, hydrogen forms diatomic molecules in its elemental state, unlike the alkali metals which exist as monatomic species.

Assuming that the questioner meant "trifluoride" instead of "trifluride", there are four total atoms in the formula unit, AsF3.

In most database management systems, you can modify field properties in a table by using the ALTER TABLE statement followed by the MODIFY COLUMN clause. This allows you to change parameters such as data type, size, nullability, and constraints for a specific field in the table. Remember to ensure that any modifications do not violate existing data integrity rules.

Molecular compounds are typically formed between nonmetals, which are found on the right side of the periodic table. This includes groups 14-18, known as the carbon group, nitrogen group, oxygen group, halogens, and noble gases. These elements tend to share electrons to form covalent bonds, creating molecules.

Cobalt: Its atomic number, which equals the number of protons in its nucleus, is 27.

A sacrificial table is typically referred to as an altar. It is a flat-topped structure used for religious or ceremonial purposes, often involving offerings or sacrifices.

He in the periodic table refers to Helium. Helium is a noble gas with the atomic number 2 and is the second lightest element in the periodic table. It is commonly used in balloons and for cooling in cryogenics.

The energy of the valence shell remains the same.

It is an isotope that occurs in nature, and is not manmade. Isotopes, by the way, are atoms that have the same number of protons, but different number of neutrons. The atomic number is the same, but atomic weight (or mass) is different. For instance, Carbon can be Carbon 10, 11, 12, or 14. They are all carbon.

The halogens are a group of elements on the Periodic Table (group 17/7A) which are all highly reactive non-metals. They consist of fluorine (F), chlorine (Cl), Bromine (Br), and Iodine (I). Astatine (At) is also in that group, but is rarely encountered in chemistry. They are unique because the first four referred to above are all diatomic, which means they exist in nature as a diatomic molecule with a single covalent bond. Because they have seven valence electrons, the octet rule says they only need to acquire one more to achieve a full valence shell. This means they are one of the most reactive groups of elements, and they react readily with most metals.

The noble gases, in column 18 (or in older tables, column VIII) do not bond, they already have full set of electrons. the rest all bond because they want full set of electrons to be more stable.