1. When Mendeleyev arranged the elements into the periodic table, he found that elements with

fell into groups on the table

A. the same mass
B. similar size
C. Similar properties
D. The same color

2. Every element has its own atomic number. The atomic number is the number of in the nucleus of an atom of the element
A. electrons
B. Neutrons
C. Positrons
D. Protons

3. In the modern periodic table, elements are arranged according to increasing .
A. Atomic number
B. Atomic mass
C. date of discovery
D. Electrical conductivity

My answers
1. B
2. D
3. A

I agree with 2 and 3.

1) should similar properties

One column has the noble gases for example. They are all different sizes, but have similar properties.

Thank you so much!!!

1. To determine which option is correct for the first question, we need to understand how Mendeleev arranged the elements in the periodic table. Mendeleev organized the elements based on their properties and patterns. Elements with similar properties were placed in the same group or column on the table.

Knowing this, we can analyze the given options:
A. The same mass: This option can be eliminated, as Mendeleev arranged elements based on properties, not mass.
B. Similar size: This option is a possibility, as elements with similar properties often have similar atomic sizes.
C. Similar properties: This option aligns with Mendeleev's arrangement principle, as elements with similar properties were grouped together.
D. The same color: This option has nothing to do with Mendeleev's arrangement of elements.

Thus, the correct answer for the first question is C. Similar properties.

2. The atomic number of an element represents the number of protons in the nucleus of an atom of the element. Therefore, the correct answer for the second question is D. Protons.

3. In the modern periodic table, elements are arranged according to increasing atomic number. The atomic number indicates the number of protons in the nucleus of an atom. Therefore, the correct answer for the third question is A. Atomic number.

Your answers are correct:
1. B (Similar properties)
2. D (Protons)
3. A (Atomic number)