Helium - 4 isotope has 2 protons and 2 neutrons.
Its atomic number is 2 (the number of protons). Atomic number is the number of protons in the atom of an element and it identifies the element. All the isotopes of an element have the same atomic number (same number of protons). So, all the isotopes of hellium have 2 protons.
The number 4 that identifies the helium - 4 isotope is the mass number, i.e. the number of protons plus the number of neutron. So, helium-4 isotope has 2 protons and 2 neutrons. While, other isotopes of helium have 2 protons but different number of neutrons.
The atomic number enable us to deduce the number of electrons in an atom because the atoms are neutral, which implies that the positive and negative charge are equal. Given that the magnitude of the charge of electons and protons are equal but the sign is opposed (protons are positve and electrons are negative) the number of electrons in the atom equals the number of protonts. That is why the atomic number is also the number of electrons of the atom.
Answer: A closed system, because energy can enter or leave the container, but the water molecules cannot
Explanation:
Open system: In this system energy and matter both have access to their surroundings beyond the boundaries of system. .
Closed system :In this type system only energy has an access to its surroundings beyond the boundaries of system but not matter.
Isolated system:In this type system exchange of both energy and matter are restricted to move outside the boundaries of system.
According to question, the system given is a closed system because energy is transferred from the burner to glass flask and from the glass flask to the water (matter). But water molecules are only getting condensed on the inside surface of the flask that is exchange of matter beyond the boundaries of the system is restricted. Hence, closed system ,A closed system, because energy can enter or leave the container, but the water molecules cannot.
Answer:
b. 4.4
Explanation:
pH is related to the concentration of H₃O⁺ through the following equation:
pH = -log([H₃O⁺]) = -log(4 x 10⁻⁵)
pH = 4.4
The correct answer is false. The statement given does not describe a property in general. However, it speaks of a specific type of property which is the physical property. This property is the one that does not change the identity of a substance. A property can also be a chemical property where the identity of a substance is changed.
The answer is 3). This is because elements are the simplest form of a substance, and cannot be broken down any further. Compounds on the other hand are much more complex than elements and can be broken down INTO elements.
For example, Na, sodium, is an element and cannot be broken down further. H2O, water, is a compound and can be broken down into Hydrogen and Oxygen.
