Which property best distinguishes a metal from a non-metal in the periodic table?

1. Metals sit on the left and centre of the table. 2. They have few valence electrons and lose them easily. 3. Losing electrons makes metals positive cations. 4. Non-metals sit on the right of the table. 5. They have many valence electrons and gain electrons to fill their octet. 6. So the electron transfer tendency cleanly separates metals from non-metals. 7. Atomic mass and proton count do not split metals from non-metals in any simple way. _Source: Selina Concise Chemistry ICSE Class 10, Ch 1 'Periodic Table' (aplustopper.com extract)_